Paleobiología de los peces amiiformes del Cretácico Inferior de Las Hoyas: Una aproximación multidisciplinar integradora

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 12-06-2015The fossil record of the Early Cretaceous (Barremian) of Las Hoyas includes three taxa of amiiform fishes. These taxa, traditionally assigned to the species Caturus tarraconensis, Amiopsis woodwardi and Vidalamia catalunica, represent actually three new species. These species are the basis for a multidisciplinary study whose objective is to comprehend the palaeobiology of these fishes in the context of a wetland ecosystem. From a phylogenetic point of view, one of the species represents a primitive lineage, with a mosaic combination of characters from both caturoids and amioids. The second species is classified as plesion Vidalamiinae, and the third one as a member of this same subfamily. A palaeobiogeographic study of the order Amiiformes, including the three species from Las Hoyas, shows that the record of this group extends from at least the Early Jurassic to Recent times, reaching its maximum diversity during the Cretaceous. Its historical distribution is mainly explained by a series of vicariant events that originated from the Tethys Sea. The osseochronometric analysis of the growth cessation marks detected in the scales of the three species shows that they presented different growth profiles. Growth of amiiform fishes seems to have a phylogenetic component, and to be strongly influenced by environmental conditions, especially temperature. Actuotaphonomical experimentation of decay in extant fish carcasses confirms that a freshwater environment favors a severe degradation of tissues. In consequence, the presence of a protection mechanism, such as microbial mats, is needed to justify the exceptional preservation of the fossil record from Las Hoyas. Additionally, this experimentation shows that carcasses suffer abrasion by transport even in very low energy systems. Absence of evidence of abrasion in the amiiform fossil fishes of Las Hoyas suggests that their association at this site is autochthonous in origin. The autochthony of the association allows to interpret the sample of each of the three species as representative of their original populations. An analysis of the population structure of these species shows that they presented habitat partitioning: juvenile and adult individuals did not inhabit the same environment. The ecological role played by the three species in the palaeowetland of Las Hoyas would be different both ontogenetically within each species and interspecificallyEl registro fósil del Cretácico Inferior (Barremiense) de Las Hoyas incluye tres taxa de peces amiiformes. Dichos taxa, tradicionalmente asignados a las especies Caturus tarraconensis, Amiopsis woodwardi y Vidalamia catalunica, representan, sin embargo, tres especies nuevas. Estas tres especies son la base de un estudio multidisciplinar que tiene por objetivo comprender su paleobiología en el contexto de un ecosistema de tipo wetland. Desde un punto de vista filogenético, una de las especies representa un linaje primitivo, con una combinación en mosaico de caracteres de caturoideos y amioideos. La segunda especie es clasificada como plesión Vidalamiinae, y la tercera como un miembro de esta misma subfamilia. Un estudio paleobiogeográfico del orden Amiiformes, incluyendo las tres especies de Las Hoyas, muestra que el registro de este grupo se extiende al menos desde el Jurásico Inferior hasta nuestros días, alcanzando su máxima diversidad durante el Cretácico. Su distribución histórica se explica fundamentalmente en base a eventos de vicarianza que tuvieron en el Mar de Tethys su centro de origen. El análisis oseocronométrico de las marcas de parada de crecimiento detectadas en las escamas de las tres especies muestra que éstas presentaban patrones de crecimiento diferentes. El crecimiento de los peces amiiformes parece tener un componente filogenético, y estar fuertemente ligado a las condiciones ambientales, especialmente a la temperatura. Un estudio de experimentación actuotafonómica de descomposición de carcasas de peces actuales confirma que un ambiente dulceacuícola favorece una severa degradación de los tejidos. En consecuencia, debió existir un mecanismo de protección, como el crecimiento de tapetes microbianos, que permitiese la excepcional preservación del registro fósil de Las Hoyas. Además, la experimentación demuestra que las carcasas sufren procesos de abrasión por transporte incluso en sistemas de muy baja energía; la ausencia de indicios de abrasión en los peces amiiformes de Las Hoyas sugiere que su asociación en este yacimiento es de origen autóctono. La autoctonía de esta asociación permite interpretar la muestra de cada una de las tres especies de amiiformes como representativas de sus poblaciones originales. El análisis de la estructura poblacional de estas especies demuestra que éstas presentaban división de hábitats: los juveniles y adultos no habitaban en el mismo ambiente. El papel ecológico de las tres especies en el paleohumedal de Las Hoyas sería distinto tanto ontogenéticamente para cada especie como interespecíficament

Osteology and relationships of Captorhinus aguti (Cope) (Reptilia: Captorhinomorpha)

80 p., 38 fig.http://paleo.ku.edu/contributions.htm

Phylogeny of the limbed vertebrates with special consideration of the origin of the modern amphibians

Trotz Jahrzehnten intensiver Forschung bleiben die Ursprünge der Frösche einschließlich Kröten und Unken (Salientia), Salamander einschließlich Molche (Caudata) und Blindwühlen (Gymnophiona), zusammen mit dem der ausgestorbenen Albanerpetontidae, kontrovers. Drei Gruppen von Hypothesen halten sich in der Literatur: Erstens könnten die erwähnten Taxa ein Monophylum bilden (Lissamphibia, eine Kronengruppe, von der Albanerpetontidae ein Mitglied oder die Schwestergruppe sein könnte), das in den paläozoischen Temnospondylen verschachtelt sein könnte, was aus den Lepospondylen des gleichen Zeitalters Stammgruppenamnioten machen würde (Temnospondylenhypothese/TH). Zweitens könnte Lissamphibia zu den Lepospondylen gehören; in diesem Fall wären die Temnospondylen Stammgruppentetrapoden (Lepospondylenhypothese/LH). Alternativ dazu könnten die Frösche und die Salamander Temnospondylen sein, während die Blindwühlen Lepospondylen wären (Polyphyliehypothese/PH). Ich habe versucht, zwischen diesen Alternativen sowohl direkt (durch phylogenetische Analyse) als auch indirekt zu unterscheiden (die PH sagt ein viel älteres Divergenzdatum zwischen den modernen Amphibien voraus als das Alter, das sowohl die TH als auch die LH implizieren). Drei zum Teil neuartige Datierungsmethoden stützen ein permisches Alter; das ist mit der TH und der LH vereinbar, aber nicht mit der PH. Diese Methoden sind: ein mit neuer Software erstellter und analysierter sowie an der Zeit kalibrierter Supertree; molekulare Divergenzdatierung mit mehreren Kalibrierungspunkten, deren maximales Alter beschränkt ist; und Berechnung von Konfidenzintervallen auf das Ursprungsdatum eines Monophylums – letztere Methode ist unabhängig von der Phylogenie und verwendet ausschließlich stratigraphische Daten. Alle drei Hypothesen werden von vor kurzem veröffentlichten phylogenetischen Analysen unterstützt. Ich habe Änderungen an drei Datenmatrizen vorgenommen, die die TH oder die PH gestützt hatten, um sie in Übereinstimmung mit der beschreibenden Literatur und eigenen Beobachtungen zu bringen, potentiell kontinuierliche Merkmale geordnet, korrelierte Merkmale zusammengelegt, und von der Ontogenie beeinflusste Merkmale in morphologisch nicht ausgewachsenen Exemplaren als unbekannt codiert; wenn ich sie neu analysiere, stützen diese Matrizen (einschließlich der größten bisher veröffentlichten, die die TH aufrecht erhalten hatte) die LH. Das stimmt mit früheren Ergebnissen überein, wonach kleine Änderungen an einer Datenmatrix große Unterschiede in den resultierenden Bäumen hervorrufen können. In zwei von diesen Matrizen ist die TH nur ein bisschen weniger sparsam als die LH, aber die PH entspricht in allen dreien deutlich weniger dem Parsimonieprinzip. Die phylogenetische Position der Albanerpetontiden bleibt instabil.Despite decades of intensive research, the origins of the frogs incl. toads (Salientia), of the salamanders incl. newts (Caudata), and of the caecilians (Gymnophiona), together with that of the extinct Albanerpetontidae, remain controversial. Three groups of hypotheses persist in the literature: First, the aforementioned taxa could form a clade (Lissamphibia, a crown-group of which Albanerpetontidae may be a member or the sister-group), which could be nested among the Paleozoic temnospondyls, making the coeval lepospondyls stem-amniotes (temnospondyl hypothesis/TH). Second, Lissamphibia could belong among the lepospondyls; in this case, the temnospondyls would be stem-tetrapods (lepospondyl hypothesis/LH). Alternatively, the frogs and the salamanders may be temnospondyls while the caecilians may be lepospondyls (polyphyly hypothesis/PH). I have tried to discriminate between these alternatives both directly (by phylogenetic analysis) and indirectly (the PH predicts a much older divergence date between the modern amphibians than the age implied by the TH as well as the LH). Three partly novel dating methods support a Permian date, compatible with the TH and the LH but not the PH. These methods are: a time-calibrated supertree compiled and analyzed with new software; molecular divergence dating with several calibration points that have maximum age constraints; and calculation of confidence intervals on the time of origin of a clade – this latter method is independent of the phylogeny and uses stratigraphic data only. All three hypotheses have been supported by recently published phylogenetic analyses. Having made changes to three data matrices that supported the TH or the PH to make them congruent with the descriptive literature and personal observations, ordered potentially continuous characters, merged correlated characters, and scored ontogeny-affected characters as unknown in morphologically immature specimens, I find that these matrices (including the largest one published to date, which had bolstered the TH) support the LH upon reanalysis. This agrees with previous findings that small changes to a data matrix can cause large differences between the resulting trees. The TH is only a little less parsimonious than the LH in two of them, but the PH is much less parsimonious in all three. The phylogenetic position of Albanerpetontidae remains unstable

Families Bothremydidae, Euraxemydidae, and Araripemydidae.

698 p. : ill. (some col.), maps (1 col.) ; 26 cm.Includes bibliographical references (p. 657-672).Although pleurodires have been considered significantly less diverse than their sister group, the cryptodires, current discoveries show that pleurodires had a more complex and extensive evolutionary history than had been realized. Previously unknown radiations, particularly in the near-shore marine realm, are revealed by taxa with diverse cranial morphology, indicating many different feeding and sensory strategies. The pleurodire group that is changed the most by the new discoveries is its largest group, the hyperfamily Pelomedusoides. The hyperfamily Pelomedusoides now consists of the families Pelomedusidae, Podocnemididae, Bothremydidae, Araripemydidae, and Euraxemydidae, new family. The families Bothremydidae, Araripemydidae, and Euraxemydidae, new family, are documented with descriptions of skulls, lower jaws, and shells. The relationships of the family Podocnemididae to its sister taxa Hamadachelys and Brasilemys are recognized by placing them in the epifamily Podocnemidinura. The epifamily Podocnemidinura is the sister group to the family Bothremydidae, and together they form the superfamily Podocnemidoidea. The family Araripemydidae consists of one taxon, Araripemys barretoi, from the Aptian-Albian of Brazil. Description of new cranial material suggests that it is the sister group to all other Pelomedusoides or the sister group to the Pelomedusidae, but these relationships are only weakly supported. There is strong support for a multichotomy of Araripemys, Pelomedusidae, and remaining Pelomedusoides. Araripemys is characterized by very thin triturating surfaces and by a shell that lacks mesoplastra and has the first costals reaching the shell margin. The new family Euraxemydidae consists of two new genera: Euraxemys essweini, n. gen. et sp., from the Albian Santana Formation of Brazil, and Dirqadim schaefferi, n. gen. et sp., from the Cenomanian Kem Kem beds of Morocco. Members of the Euraxemydidae are united by the unique possession of a medial process of the quadrate partially covering the prootic and narrowly contacting a ventral process of the exoccipital, in contrast to all other pleurodires, which have either complete exposure or complete covering of the prootic ventrally. Furthermore, members have a ventral process of the exoccipital that is exposed at the lateral margin of the basioccipital in an elongate foot. The Euraxemydidae is hypothesized as the sister group to the superfamily Podocnemidoidea. The family Bothremydidae and the epifamily Podocnemidinura (consisting of the family Podocnemididae, Hamadachelys, and Brasilemys) are united as the superfamily Podocnemidoidea based on the possession of a quadrate-basioccipital contact, the complete or nearly complete ventral covering of the prootic, and the extension of the pectoral scales onto the entoplastron. The family Bothremydidae is a large and diverse group extending from the Albian to the Eocene in North and South America, Europe, Africa, and India. Its monophyly is supported by the presence of a wide exoccipital-quadrate contact, a eustachian tube separated from the incisura columellae auris usually by bone to form a bony canal for the stapes, absence of a fossa precolumellaris, a supraoccipital--quadrate contact (except in the tribe Taphrosphyini), and a posterior enlargement of the fossa orbitalis. Although there is a diversity of triturating surfaces within the family, primitively bothremydids have a posteriorly wide triturating surface with a significant palatine contribution in the upper jaw. The family Bothremydidae consists of four newly recognized, monophyletic groups: the tribes Kurmademydini, Cearachelyini, Bothremydini, and Taphrosphyini. The tribe Kurmademydini consists of two taxa: Kurmademys kallamedensis, from the Maastrichtian Kallamedu Formation of India, and Sankuchemys sethnai, from the Maastrichtian Intertrappean beds of India. The tribe Kurmademydini is characterized by extensive temporal and cheek emargination, a large fossa precolumellaris, and a small, anterior exposure of the prootic on the ventral surface. The tribe Kurmademydini is the sister group to the subfamily Bothremydinae (consisting of the tribes Cearachelyini, Bothremydini, and Taphrosphyini). Members of the subfamily Bothremydinae all possess a foramen stapedio-temporale that faces anteriorly. The tribe Cearachelyini consists of Cearachelys placidoi, from the Albian Santana Formation of Brazil, and Galianemys emringeri and Galianemys whitei, both from the Cenomanian Kem Kem beds of Morocco. The tribe Cearachelyini is characterized by a jugal retracted from the orbital margin and a fenestra postotica formed into a short slit. The tribe Cearachelyini is the sister group to the infrafamily Bothremydodda (consisting of the tribes Bothremydini and Taphrosphyini). The infrafamily Bothremydodda is characterized by a quadrate shelf formed below the cavum tympani, a foramen stapedio-temporale and foramen nervi trigemini that are very close together on the anterior face of the otic chamber, and a condylus occipitalis and occipital neck that are formed only by the exoccipitals. The tribe Bothremydini consists of Foxemys mechinorum, from the Campanian-Maastrichtian of France; Polysternon provinciale, from the Campanian of Europe; Zolhafah bella, from the Maastrichtian Dakla Formation of Egypt; Rosasia soutoi, from the Campanian-Maastrichtian of Portugal; Araiochelys hirayamai, n. gen. et sp., from the Danian phosphates of Ouled Abdoun Basin, Morocco; Bothremys cooki, from the Maastrichtian Navesink Formation of New Jersey; Bothremys maghrebiana, n. sp., from the Danian phosphates of Ouled Abdoun Basin, Morocco; Bothremys kellyi, n. sp., from the Ypresian phosphates of Ouled Abdoun Basin, Morocco; Bothremys arabicus, from the Santonian of Jordan; Chedighaii hutchisoni, n. gen. et sp., from the Campanian Kirtland Formation of New Mexico; and Chedighaii barberi, n. gen., from the Campanian of Arkansas, Alabama, Kansas, and New Jersey. The tribe Bothremydini is the sister group to the tribe Taphrosphyini. The tribe Taphrosphyini is characterized by the presence of a jugal-quadrate contact, the absence of a maxilla-quadratojugal contact, and the absence of a supraoccipital-quadrate contact. Members of the tribe Taphrosphyini have a considerable variety of triturating surfaces but they lack the wide, triangular surfaces typical of the other bothremydids. The tribe Taphrosphyini consists of Taphrosphys sulcatus, from the Danian Hornerstown Formation of New Jersey; Taphrosphys congolensis, from the Paleocene of Cabinda, west Africa; Taphrosphys ippolitoi, n. sp., from the Danian phosphates of the Ouled Abdoun Basin, Morocco; Labrostochelys galkini, n. gen. et sp., from the Danian phosphates of the Ouled Abdoun Basin, Morocco; Phosphatochelys tedfordi, from the Ypresian phosphates of the Ouled Abdoun Basin Morocco; Ummulisani rutgersensis, n. gen. et sp., from the Ypresian phosphates of the Ouled Abdoun Basin, Morocco; Rhothonemys brinkmani, n. gen. et sp., from the Paleogene phosphates of the Ouled Abdoun Basin, Morocco; Azabbaremys moragjonesi, from the Paleocene Teberemt Formation of Mali; Nigeremys gigantea, from the Maastrichtian of Niger; and Arenila krebsi, from the Maastrichtian Dakla Formation of Egypt. Among the Bothremydidae, the Taphrosphyini is the most diverse morphologically. The triturating surfaces show a wide range of variation. The long, narrow skull of Labrostochelys differs significantly from the very short skull of Phosphatochelys. Other genera, such as Azabbaremys and Arenila, have large and massive skulls, but without broadly expanded triturating surfaces, while Ummulisani has very narrow and deep labial ridges. The nasal regions of Taphrosphyini also show wide diversity. Rhothonemys has nasal openings and cavities more than twice the size of the orbits, but the nasal openings in Labrostochelys are smaller than the relatively small orbits. This diversity of Taphrosphyini skull morphology is mostly evident in the Paleogene of North Africa. A phylogenetic analysis of the core dataset of 41 taxa, 122 cranial characters, and 52 postcranial characters relies on comparative descriptions of these taxa. The analysis using PAUP results in one most parsimonious cladogram of 382 steps with a consistency index of 0.6. A Bremer decay analysis shows that the family Bothremydidae is strongly supported at five steps: the tribes Kurmademydini and Cearachelyini have an index of 2, and the tribe Taphrosphyini has an index of 3. The tribe Bothremydini becomes unresolved at one step and is the most weakly supported of these groups. The addition of selected shell-only taxa with low missing data values to the core dataset results in one equally parsimonious cladogram that is resolved as: (Proterochersis (Platychelyidae (Dortoka (Chelidae (Pelomedusidae + Araripemys) (Euraxemydidae (Teneremys (Podocnemididae + Hamadachelys + Brasilemys (Bothremydidae)))))))). A partitioned dataset consisting only of cranial characters (excluding all shell-only taxa) results in one equally parsimonious cladogram identical to the most parsimonious cladogram resulting from the whole dataset; however, a partitioned dataset consisting only of postcranial characters (excluding all skull-only taxa) resulted in 2704 trees, the consensus of which lacks resolution for nearly all Pelomedusoides, but which does resolve more basal pleurodires. When the skull morphology of the Bothremydidae is placed in the context of all other turtles, it becomes apparent that this family has the greatest range of skull forms of any turtle family yet known. In fact, the skull morphologies of many turtle families seem remarkably uniform in comparison (e.g., Testudinidae, Kinosternidae, Pelomedusidae, Trionychidae, Carettochelyidae)...There are other turtle families with bizarre skull morphologies (e.g., Nanhsiungchelyidae; Meiolaniidae) but these are not taxonomically diverse, at least as they are now known. In no other family do we see the extremes exemplified by the skulls of forms like Cearachelys, Bothremys, Labrostochelys, Azzabaremys, Rhothonemys, and Phosphatochelys. It is this remarkable variation in skull morphology that has allowed us to formulate a strong hypothesis of bothremydid relationships in spite of the presence in Pelomedusoides of remarkably uniform shells"--P. 6-8

Families Bothremydidae, Euraxemydidae, and Araripemydidae.

698 p. : ill. (some col.), maps (1 col.) ; 26 cm.Includes bibliographical references (p. 657-672).Although pleurodires have been considered significantly less diverse than their sister group, the cryptodires, current discoveries show that pleurodires had a more complex and extensive evolutionary history than had been realized. Previously unknown radiations, particularly in the near-shore marine realm, are revealed by taxa with diverse cranial morphology, indicating many different feeding and sensory strategies. The pleurodire group that is changed the most by the new discoveries is its largest group, the hyperfamily Pelomedusoides. The hyperfamily Pelomedusoides now consists of the families Pelomedusidae, Podocnemididae, Bothremydidae, Araripemydidae, and Euraxemydidae, new family. The families Bothremydidae, Araripemydidae, and Euraxemydidae, new family, are documented with descriptions of skulls, lower jaws, and shells. The relationships of the family Podocnemididae to its sister taxa Hamadachelys and Brasilemys are recognized by placing them in the epifamily Podocnemidinura. The epifamily Podocnemidinura is the sister group to the family Bothremydidae, and together they form the superfamily Podocnemidoidea. The family Araripemydidae consists of one taxon, Araripemys barretoi, from the Aptian-Albian of Brazil. Description of new cranial material suggests that it is the sister group to all other Pelomedusoides or the sister group to the Pelomedusidae, but these relationships are only weakly supported. There is strong support for a multichotomy of Araripemys, Pelomedusidae, and remaining Pelomedusoides. Araripemys is characterized by very thin triturating surfaces and by a shell that lacks mesoplastra and has the first costals reaching the shell margin. The new family Euraxemydidae consists of two new genera: Euraxemys essweini, n. gen. et sp., from the Albian Santana Formation of Brazil, and Dirqadim schaefferi, n. gen. et sp., from the Cenomanian Kem Kem beds of Morocco. Members of the Euraxemydidae are united by the unique possession of a medial process of the quadrate partially covering the prootic and narrowly contacting a ventral process of the exoccipital, in contrast to all other pleurodires, which have either complete exposure or complete covering of the prootic ventrally. Furthermore, members have a ventral process of the exoccipital that is exposed at the lateral margin of the basioccipital in an elongate foot. The Euraxemydidae is hypothesized as the sister group to the superfamily Podocnemidoidea. The family Bothremydidae and the epifamily Podocnemidinura (consisting of the family Podocnemididae, Hamadachelys, and Brasilemys) are united as the superfamily Podocnemidoidea based on the possession of a quadrate-basioccipital contact, the complete or nearly complete ventral covering of the prootic, and the extension of the pectoral scales onto the entoplastron. The family Bothremydidae is a large and diverse group extending from the Albian to the Eocene in North and South America, Europe, Africa, and India. Its monophyly is supported by the presence of a wide exoccipital-quadrate contact, a eustachian tube separated from the incisura columellae auris usually by bone to form a bony canal for the stapes, absence of a fossa precolumellaris, a supraoccipital--quadrate contact (except in the tribe Taphrosphyini), and a posterior enlargement of the fossa orbitalis. Although there is a diversity of triturating surfaces within the family, primitively bothremydids have a posteriorly wide triturating surface with a significant palatine contribution in the upper jaw. The family Bothremydidae consists of four newly recognized, monophyletic groups: the tribes Kurmademydini, Cearachelyini, Bothremydini, and Taphrosphyini. The tribe Kurmademydini consists of two taxa: Kurmademys kallamedensis, from the Maastrichtian Kallamedu Formation of India, and Sankuchemys sethnai, from the Maastrichtian Intertrappean beds of India. The tribe Kurmademydini is characterized by extensive temporal and cheek emargination, a large fossa precolumellaris, and a small, anterior exposure of the prootic on the ventral surface. The tribe Kurmademydini is the sister group to the subfamily Bothremydinae (consisting of the tribes Cearachelyini, Bothremydini, and Taphrosphyini). Members of the subfamily Bothremydinae all possess a foramen stapedio-temporale that faces anteriorly. The tribe Cearachelyini consists of Cearachelys placidoi, from the Albian Santana Formation of Brazil, and Galianemys emringeri and Galianemys whitei, both from the Cenomanian Kem Kem beds of Morocco. The tribe Cearachelyini is characterized by a jugal retracted from the orbital margin and a fenestra postotica formed into a short slit. The tribe Cearachelyini is the sister group to the infrafamily Bothremydodda (consisting of the tribes Bothremydini and Taphrosphyini). The infrafamily Bothremydodda is characterized by a quadrate shelf formed below the cavum tympani, a foramen stapedio-temporale and foramen nervi trigemini that are very close together on the anterior face of the otic chamber, and a condylus occipitalis and occipital neck that are formed only by the exoccipitals. The tribe Bothremydini consists of Foxemys mechinorum, from the Campanian-Maastrichtian of France; Polysternon provinciale, from the Campanian of Europe; Zolhafah bella, from the Maastrichtian Dakla Formation of Egypt; Rosasia soutoi, from the Campanian-Maastrichtian of Portugal; Araiochelys hirayamai, n. gen. et sp., from the Danian phosphates of Ouled Abdoun Basin, Morocco; Bothremys cooki, from the Maastrichtian Navesink Formation of New Jersey; Bothremys maghrebiana, n. sp., from the Danian phosphates of Ouled Abdoun Basin, Morocco; Bothremys kellyi, n. sp., from the Ypresian phosphates of Ouled Abdoun Basin, Morocco; Bothremys arabicus, from the Santonian of Jordan; Chedighaii hutchisoni, n. gen. et sp., from the Campanian Kirtland Formation of New Mexico; and Chedighaii barberi, n. gen., from the Campanian of Arkansas, Alabama, Kansas, and New Jersey. The tribe Bothremydini is the sister group to the tribe Taphrosphyini. The tribe Taphrosphyini is characterized by the presence of a jugal-quadrate contact, the absence of a maxilla-quadratojugal contact, and the absence of a supraoccipital-quadrate contact. Members of the tribe Taphrosphyini have a considerable variety of triturating surfaces but they lack the wide, triangular surfaces typical of the other bothremydids. The tribe Taphrosphyini consists of Taphrosphys sulcatus, from the Danian Hornerstown Formation of New Jersey; Taphrosphys congolensis, from the Paleocene of Cabinda, west Africa; Taphrosphys ippolitoi, n. sp., from the Danian phosphates of the Ouled Abdoun Basin, Morocco; Labrostochelys galkini, n. gen. et sp., from the Danian phosphates of the Ouled Abdoun Basin, Morocco; Phosphatochelys tedfordi, from the Ypresian phosphates of the Ouled Abdoun Basin Morocco; Ummulisani rutgersensis, n. gen. et sp., from the Ypresian phosphates of the Ouled Abdoun Basin, Morocco; Rhothonemys brinkmani, n. gen. et sp., from the Paleogene phosphates of the Ouled Abdoun Basin, Morocco; Azabbaremys moragjonesi, from the Paleocene Teberemt Formation of Mali; Nigeremys gigantea, from the Maastrichtian of Niger; and Arenila krebsi, from the Maastrichtian Dakla Formation of Egypt. Among the Bothremydidae, the Taphrosphyini is the most diverse morphologically. The triturating surfaces show a wide range of variation. The long, narrow skull of Labrostochelys differs significantly from the very short skull of Phosphatochelys. Other genera, such as Azabbaremys and Arenila, have large and massive skulls, but without broadly expanded triturating surfaces, while Ummulisani has very narrow and deep labial ridges. The nasal regions of Taphrosphyini also show wide diversity. Rhothonemys has nasal openings and cavities more than twice the size of the orbits, but the nasal openings in Labrostochelys are smaller than the relatively small orbits. This diversity of Taphrosphyini skull morphology is mostly evident in the Paleogene of North Africa. A phylogenetic analysis of the core dataset of 41 taxa, 122 cranial characters, and 52 postcranial characters relies on comparative descriptions of these taxa. The analysis using PAUP results in one most parsimonious cladogram of 382 steps with a consistency index of 0.6. A Bremer decay analysis shows that the family Bothremydidae is strongly supported at five steps: the tribes Kurmademydini and Cearachelyini have an index of 2, and the tribe Taphrosphyini has an index of 3. The tribe Bothremydini becomes unresolved at one step and is the most weakly supported of these groups. The addition of selected shell-only taxa with low missing data values to the core dataset results in one equally parsimonious cladogram that is resolved as: (Proterochersis (Platychelyidae (Dortoka (Chelidae (Pelomedusidae + Araripemys) (Euraxemydidae (Teneremys (Podocnemididae + Hamadachelys + Brasilemys (Bothremydidae)))))))). A partitioned dataset consisting only of cranial characters (excluding all shell-only taxa) results in one equally parsimonious cladogram identical to the most parsimonious cladogram resulting from the whole dataset; however, a partitioned dataset consisting only of postcranial characters (excluding all skull-only taxa) resulted in 2704 trees, the consensus of which lacks resolution for nearly all Pelomedusoides, but which does resolve more basal pleurodires. When the skull morphology of the Bothremydidae is placed in the context of all other turtles, it becomes apparent that this family has the greatest range of skull forms of any turtle family yet known. In fact, the skull morphologies of many turtle families seem remarkably uniform in comparison (e.g., Testudinidae, Kinosternidae, Pelomedusidae, Trionychidae, Carettochelyidae)...There are other turtle families with bizarre skull morphologies (e.g., Nanhsiungchelyidae; Meiolaniidae) but these are not taxonomically diverse, at least as they are now known. In no other family do we see the extremes exemplified by the skulls of forms like Cearachelys, Bothremys, Labrostochelys, Azzabaremys, Rhothonemys, and Phosphatochelys. It is this remarkable variation in skull morphology that has allowed us to formulate a strong hypothesis of bothremydid relationships in spite of the presence in Pelomedusoides of remarkably uniform shells"--P. 6-8

Systematics and morphology of American mosasaurs (Reptilia, Sauria)

Mosasaurs were large, marine platynotan lizards which became abundant and diversified during the latter half of Cretaceous time, but disappeared at the close of the period….https://elischolar.library.yale.edu/peabody_museum_natural_history_bulletin/1022/thumbnail.jp

High latitude Gondwanan famennian biodiversity patterns : evidence from the South African Witpoort Formation (Cape Supergroup, Witteberg Group)

Ph.D. Faculty of Science, University of the Witwatersrand, 2011Reassessment of the stratigraphic position of the Waterloo Farm black shale from Grahamstown, South Africa, revealed that it is situated in the uppermost Witpoort Formation, as opposed to the middle of the Witpoort Formation as previously reported. This argillaceous unit appears to be contemporaneous with globally correlated black anaerobic sediments intimately associated with the Hangenberg Extinction, the final and most important pulse of the end Devonian extinction event. The Waterloo Farm fauna is one of only seven significant faunas from the end Famennian, and one of only two from Gondwana. The other one, from Morocco, was situated in the palaeotropics of northern Gondwana whereas Waterloo Farm, situated near the palaeo South Pole, provides the only high latitude locality. Extensive fieldwork resulted in 511 catalogued fossil fish specimens. These comprise at least 21 taxa of which least 2 are agnathan, 7 placoderm, 4 acanthodian, 2 chondrichthyan, 1 actinopterygian and 5 sarcopterygian. Sarcopterygians include an onychodont, a coelacanth, a tristichopterid and an isolated cleithrPriscomyzon riniensis, the oldest lamprey, exhibits many of the key specialisations of modern lampreys including a large oral disc, circumoral teeth and a branchial basket. Analysis of Priscomyzon revealed that lampreys are ancient specialists that, having acquired key specialisations before the end of the Devonian period, survived with relatively little change for 360 million years. Shark fossils include Antarctilamna ultima (sp. nov.), a new species of a Gondwanan genus previously considered to have gone extinct before the late Devonian, and Plesioselachus doryssa. These taxa are basal to the crowngroup chondrichthyan radiation and provide insight into the primitive condition of chondrichthyans. A new coelacanth species, Paradiplocercides kowiensis (gen. et sp. nov.), represents one of the most completely preserved early coelacanths and offers insights into the early diversification of coelacanths, and sequences of morphologicalum of an advanced stem group tetrapodomorph close to the elpistostegalian grade. Priscomyzon riniensis, the oldest lamprey, exhibits many of the key specialisations of modern lampreys including a large oral disc, circumoral teeth and a branchial basket. Analysis of Priscomyzon revealed that lampreys are ancient specialists that, having acquired key specialisations before the end of the Devonian period, survived with relatively little change for 360 million years. Shark fossils include Antarctilamna ultima (sp. nov.), a new species of a Gondwanan genus previously considered to have gone extinct before the late Devonian, and Plesioselachus doryssa. These taxa are basal to the crowngroup chondrichthyan radiation and provide insight into the primitive condition of chondrichthyans. A new coelacanth species, Paradiplocercides kowiensis (gen. et sp. nov.), represents one of the most completely preserved early coelacanths and offers insights into the early diversification of coelacanths, and sequences of morphological changes in the early part of the coelacanth phylogenetic tree. Analyses of relative abundance of taxa at Waterloo Farm demonstrate a significant taphonomic filter in favour of organisms with numerous large bony elements and the resultant inappropriateness of extrapolating population structure from conventional methodologies. Exclusion of specimens derived from hard tissue alone, as well as those from single taxon death assemblages, produced a result more likely to reflect population structure, being more consistent with extrapolated trophic levels. Comparison of the Waterloo Farm fauna fossils with those from the earlier Devonian Bokkeveld Group and overlying lower Cindicates a distinctive Agulhas Sea faunal province. The Agulhas Sea fauna is the highest latitude Devonian faunal region, having existed, in a near polar setting, in the semi enclosed Agulhas Sea. This fauna inherited much of its diversity from a mid Devonian Agulhas Sea fauna characterised by Gondwanan endemic sharks, gyracanthid acanthodians and phlyctaeniid arthrodire placoderms, but lacking many taxa, which characterise other mid Devonian Gondwanan successions. The approach of Laurussia to Gondwana towards the end of the Devonian permitted an exchange of marginal marine taxa, which were previously separated by deep oceans with anoxic bottom waters. Together with moderation of global climatic gradients, this allowed augmentation of the mid Devonian relict population inhabiting the Agulhas Sea, during the Late Devonian. New faunal elements from Laurussia and eastern Gondwana resulted in a diverse, though unique, fauna with many characteristic Late Devonian taxonomic groups incapable of penetrating this high latitude environment. The Aguhlas Sea fauna was nonetheless subject to exactly the same endarboniferous Witteberg Group, as well as published records from parts of South America and Antarctica that also bounded the Agulhas Sea during this time, Devonian extinction profile as tropical coastal and temperate deep-sea environments. The abrupt nature of this event, at the end of the Famennian, is evidenced by the presence of various taxa from Waterloo Farm, formerly thought to have gone extinct before the Famennian. The Agulhas shark, Plesioselachus and the acanthodian Gyracanthides were the only members of this fauna to survive the Hangenberg extinction event. During the Carboniferous the Agulhas Sea was repopulated by a diverse actinopterygian fauna with Laurussian affinities

The Functional Morphology of Ingestion in the Platyrrhine Sclerocarpic Harvesters (Platyrrhini, Primates)

The identification of anatomical correlates of diet and feeding behavior in nonhuman primates is an important area of research in biological anthropology. The morphology of the jaws and teeth reflects the phylogeny and adaptations that distinguish taxa and their different ecological niches. Studying the form-function relationships of jaws and teeth in modern species provides a framework for interpreting the diets of extinct species and for inferring the ecological pressures that may have contributed to the evolutionary diversification of primate craniodental morphology. Previous work on modeling primate jaw mechanics has focused largely on the functional context of a closed jaw. Little attention has been given to the biomechanical arrangement of the system’s ingestive morphology whereby the anterior teeth and the musculoskeletal anatomy function in open-jaw positions. This dissertation advances the state of knowledge of the evolution of the primate feeding apparatus by considering the functional significance of the morphology of the anterior teeth, masticatory muscles and the jaws as they would operate in an open-gape context. The taxonomic focus of this thesis is a group of platyrrhines characterized by an intensive form of ingestion. These “sclerocarpic harvesters” include the pitheciids Cacajao, Chiropotes,Pithecia,andCallicebus, and also the cebid Aotus. These primates feed on fruits with hard or tough outer coverings, and the pitheciins (Cacajao, Chiropotes, Pithecia) frequently prey on the variably soft seeds within. By comparing these taxa with other platyrrhines, this research aims to to shed light on the possibility of biomechanical tradeoffs favoring either the ingestion or mastication of foods that may reflect adaptive priorities in the feeding complex, optimized for a particular set of functions. As a group, the sclerocarpic harvesters exhibit deep mandibles with expanded gonial regions where two adductors of the jaw insert, i.e., the superficial masseter and medial pterygoid muscles. These taxa are distinguished dentally from similarly-sized platyrrhines by their relatively large incisors, tall and narrow among the pitheciids, broad in Aotus, similarly used for scraping and scoring the outer protective rinds and/or gouging out the soft flesh from within hard-skinned fruits. The pitheciins are further distinguished in having robust triquetrous canine teeth – approximately triangular in cross-section – that are used to breach and pry open relatively large whole fruit with wide open jaws. Together the mandible and the canine teeth are two structures in the feeding complex that particularly distinguish the sclerocarpic harvesters and form the basis of this research. Jaw shape is routinely used in discussions of relationships among living and extinct platyrrhines, though few efforts have aimed to parse the phylogenetic and functional signals that affect the variability in this morphology. Chapter 3 of this dissertation begins the analytical section of this work by testing for functional correlates of the mandibular morphology that largely distinguish the pitheciids from the predominately-frugivorous, and similarly-sized cebids (except Aotus). 3D geometric morphometrics (3DGM) and principal components analysis was used to identify the leading sources of the variability in the shapes of 145 landmarked mandibles of pitheciids (Cacajao, Chiropotes, Pithecia, Callicebus) and cebids (Sapajus, Cebus, Aotus, Saimiri). Biomechanically-significant measurements of the mandibles were derived from the landmark coordinates, i.e., inter-landmark distances were calculated that span morphological features that aid in the mitigation of stress in the jaw during loading. These functional signals were regressed against the PCA shape components to test for correspondence between the phylogenetic and functional signals in the shapes of the jaws. Results of the 3DGM mandible study in Chapter 3 link the variability in the study sample with jaw function and distinguish these taxa in terms of feeding strategies more consistently than phylogeny. These results are support a new mechanical explanation for the diversity in jaw shape whereby Aotusand the pitheciids are unified as sclerocarpic harvesters, i.e., a group that emphasizes anterior-tooth loading during the first phase of feeding – ingestion – while the jaws of pitheciins and Sapajusoverlap in values associated with support for eccentric loading during the second phase – mastication – e.g., cracking and masticating seeds. This two-phase mechanical explanation for jaw shape diversity poses a problem for the use of mandible shape for phylogenetic analyses, particularly in platyrrhines wherein the cebids Aotusand Sapajusboth exhibit patterns of mandibular morphology that appear to reflect a process of convergence on the pitheciid-like emphasis on ingestion. However, this success in characterizing jaw shape diversity as a composite response to challenges associated with both phases of feeding suggests that a similar approach to evaluating the feeding behavior of extinct platyrrhines from fossil mandibles may add significant definition to what is known about the paleobiology of this radiation. Another component of the feeding apparatus is the musculature of the jaws, and aspects of the shape of the mandible are related to the organization the muscles. Broadly, the musculoskeletal anatomy of primate jaws is understood to be influenced by feeding behavior, phylogeny, and body size. Jaw shape and muscle anatomy act together in life but are typically studied apart, and while the discrete components of the masticatory complex provide useful insights into feeding adaptations and trends in primates, the interaction of components may not be obvious when studied in isolation. In Chapter 4, the skeletal morphology and muscle performance are integrated to study the effect of variability in jaw shape on muscle force with changes in gape. To consider the effect of body size, two larger-bodied platyrrhines were added to the comparative sample for this study, i.e., Atelesand Alouatta. Patches of virtual landmarks were applied to the attachment sites of jaw-closing muscles on 3D models of skulls using Landmark Editor software. The distances between attachments were measured with skulls set to different gape configurations, then length-tension formulas and muscle physiological cross-section area (PCSA) data from the literature were used to model maximum muscle force in each position. The results reported in Chapter 4 show that variation in muscle position with respect to the jaw joint produces a pattern of heterogeneous excursion that distinguishes each muscle, and together form patterns that are differ across the taxa studied. The relative rate of decline in muscle force outputs with increasing gape varies in the platyrrhines modeled with body size driving this relationship such that the sum of jaw muscle forces declines more gradually with increasing gape in smaller taxa while in larger taxa the decline is more acute. The scaling of the force-gape relationship with body size may therefore constitute a baseline strategy among platyrrhines to cope with the physical properties of foods that is most limiting to their ecological niche. The jaws of smaller primates favor the retention of muscle forces at higher gapes, which is consistent with the expectation that relative fruit size poses a more significant challenge for ingestion in these taxa. Conversely, larger platyrrhines exhibit a pattern that favors greater force production at lower gapes in support of diets that incorporate mastication of tougher foods that are relatively smaller on account of their greater body size. In the second half of this dissertation, the definition and functional significance of canine robusticity is explored. Robust canines are a hallmark of the pitheciin seed predators and prospective pitheciids in the fossil record exhibit similarly-robust, but more conical canines beginning in the early middle Miocene of Patagonia. Canine tooth crown height is understood more generally to correspond with diverse competitive regimes and mating strategies among primates, but little is known about the potential function of canine tooth robustness, i.e., whether proportionally wider canine teeth confer some social or dietary advantage over a more gracile crown. Canine bending strength is believed to correspond with canine tooth robusticity but does not vary with social factors such as group size and antagonism among primate species. In contrast, bending strength is higher in the robust-toothed pitheciins and capuchins (Cebusand Sapajus), several of which use these teeth for mechanically-intensive challenges associated with feeding on protected fruits and seeds. As a result, it was presumed that canine tooth robusticity is an evolutionary response to fracture risk, and it was predicted that the pitheciins and capuchins experience a lower risk of canine fracture than in other primates. In Chapter 5, the prediction that variability in canine bending strength and canine tooth robusticity corresponds with fracture risk was tested by surveying museum collections of wild caught platyrrhines of seven genera (i.e., Cacajao, Chiropotes, Pithecia, Cebus, Sapajus, Saimiri, and Ateles) for canine teeth broken before death, and then fracture rates were compared with those published for carnivores. Results demonstrate the rarity of fractured canine teeth in platyrrhines including both seed-eating and non-seed-eating species; on average one in twenty individuals exhibit one or more broken canine teeth. This consistently low prevalence of fractures among platyrrhines suggests that higher canine bending strength does not lessen the risk of breaking a canine tooth. Alternatively, it might be argued that more robust, stronger canines serve to retain a comparatively-low frequency of fracture on platyrrhines rely on these teeth to access more resistant foods. However, published surveys of carnivore fracture rates suggest that the fracture rate may vary a great deal in taxa that depend on their canine teeth for prey capture, and thus it is unlikely that primates should have resolved this problem more perfectly than carnivores. Further, primates were reported to have higher bending strength values in their canine teeth than carnivores, but the prevalence of fracture does not strictly fit this generalization. Overall the results of this study suggest that previously-reported bending strength values do not predict risk of fracture in canine teeth, and an explanation for any functional significance of variability in canine tooth robusticity is lacking. In Chapter 6, finite elements analysis (FEA) was used to evaluate an alternative hypothesis for the constraints on canine tooth shape, i.e., that the width of the cementoenamel junction (CEJ) is a response to the buildup of stresses in the surrounding alveolar tissue when the tooth is loaded during biting. A geometrically-simplified digital model of a canine crown was constructed and set in a virtual jaw bone and loaded with simulated forces, then modified in its dimensions and tested again to study the effect of changes in CEJ dimensions on the peak stresses in the modeled alveolus. Estimates of bite forces derived from published platyrrhine muscle PCSA data were used in conjunction with canine tooth measurements to model the effect of taxon-specific forces on the canine tooth model with an array of different geometry that approximates the dimensions in the platyrrhine sample (i.e., Cacajao, Chiropotes, Pithecia, Cebus, Sapajus, Saimiri, andAteles). An optimization program was run using an iterative approach to simulate the effects of different geometry and loading conditions in the modeled canines. The program identifies the geometry that best balances between the goal of minimizing the CEJ diameter (to facilitate greater mechanical advantage for penetration) while not exceeding a set stress criterion in the alveolar bone (i.e., critical failure resulting from stresses exceeding yield strength). Finally, optimized model results are compared with the dimensions of the platyrrhine sample to consider the expectation that the geometry in these taxa are the result of similar drivers and constraints as those specified in the FEA simulations. The results of FEA simulations in Chapter 6 suggest that canine shape reflects the optimization of competing pressures to maximize mechanical advantage for penetration while minimizing the stresses in the alveolar bone in which the tooth is rooted, particularly during moderate to high-gape biting. The optimized canine models generated are sensitive to the magnitude and orientation of forces applied to simulate canine biting. The models that were vertically-loaded resulted in a narrow-crowned optimal output because the stresses in these models are easily dissipated along the tooth root surface, permitting an unnaturally narrow crown without damaging the alveolar tissue. Oblique loads used to simulate biting during open-gape functions on these models produce an uneven distribution of stress in the alveolus where compressive stresses are concentrated opposite of where the oblique load is positioned. To mitigate the concentration of stresses in the alveolus, the CEJ diameter is broadened during the automated optimization process, resulting in more geometrically robust optimal output that closely approximate the dimensions of the canines from the sampled platyrrhine taxa. Strong correlations between the real geometry of the platyrrhine sample and the optimal model outputs for the obliquely-loaded trials provide support for the hypothesis that canine robusticity is a response to stress in the alveolar tissues, not the canine tooth itself. Taken together, the results of the four analytical chapters of this thesis add definition to the gross morphological patterns in the anterior teeth and jaws among the sclerocarpic harvesters, principally the pitheciins, that have been presumed to have evolved in support of their specialization on large, hard-skinned fruits and seeds. The mandibles of the pitheciids and cebids signal a malleability of mandible shape that is sensitive to mechanical challenges during both ingestion and mastication phases of feeding. However, the sclerocarpic harvesters are not exceptional in the organization of their musculature in support of ingestion at high gapes, and instead they follow a trend in the organization that scales with body size. Caveats to this observation include the special roles that canine teeth of the pitheciins and Callicebusplay as potentially different approaches to the similar problem breaching relatively large foods (i.e., tall laterally-splayed in pitheciins and shortened upright crowns in Callicebus) that may modify the force-gape relationship in the jaws by increasing the clearance and facilitating less stretch and more muscle force when biting a food of a given size. Additionally, the shape of the canine teeth themselves appear to be responses to the stresses produced during loading in the first ingestive steps when the resistant outer components of whole foods found in nature present the most intense mechanical challenges to alveolar tissue around the canines as the food is opened. Finally, while the anatomical diversity of pitheciins is related to functions that are specific to the feeding strategies among these taxa, the mechanistic relationships and biomechanical constraints on the morphology identified here are common factors in the evolution of the feeding apparatus in all primates, e.g., the yield characteristics of cortical bone and enamel, the diversity of loading regimes at different gapes, and the effect of muscle length and position on the excursion and force in jaw muscles. Thus, advances to the understanding of interactions between these factors bears significance for the evolution of feeding mechanics on a broader scale and may also benefit the evaluation of the functional morphology of the feeding complex throughout the order Primates and mammals more broadly