The history of South American octodontoid rodents and its contribution to evolutionary generalisations

Fil: Verzi, Diego Héctor. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología Vertebrados; ArgentinaFil: Morgan, Cecilia Clara. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología Vertebrados; ArgentinaFil: Olivares, Adriana Itatí. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología Vertebrados; Argentin

Systematics, phylogeny and evolutionary pattern of the hystricognath rodent <i>Eumysops</i> (Echimyidae) from the Plio–Pleistocene of southern South America

†Eumysops is a peculiar representative of the currently tropical family Echimyidae, which evolved in increasingly dry and cold Plio–Pleistocene environments of southern South America. The results of a systematic and stratigraphic review of the genus, and of phylogenetic analyses based on both morphology and a combined morphological–molecular dataset in the context of extant representatives, are presented here. Recognised diversity includes four previously described species plus a new one from the late Pliocene. These species form a well-supported monophyletic clade, sister to the late Miocene †Pampamys and the extant Thrichomys. The position of †Eumysops–†Pampamys–Thrichomys in a major clade including non-‘eumysopine’ echimyids constrains the traditional taxon Eumysopinae only to these three genera. Phylogeny and stratigraphic distribution of †Eumysops species suggest an essentially cladogenetic evolutionary pattern. Beyond this, a gradual directional change, involving increase in size and in molar hypsodonty, is shown by †Eumysops chapalmalensis as part of a late Pliocene faunal turnover interpreted as a local representation of the 2.5-Ma cooling global event. Distinctive skeletal and dental anatomy of †Eumysops, including large orbits, shortened braincase, marked hypsodonty and postcranial specialisations, would be a result of its southern history related to a particular palaeoclimatic context.Facultad de Ciencias Naturales y Muse

Phylogeny and evolutionary patterns of South American octodontoid rodents

Octodontoidea is the most diverse clade of hystricognath rodents, and is richly recorded in South America since at least the Oligocene. A parsimony-based morphological phylogenetic analysis of a wide range of extant and extinct octodontoids recovered three major clades, here recognised as Echimyidae, Octodontidae, and Abrocomidae. Taxa previously assigned to Echimyidae or Octodontoidea incertae sedis are here interpreted for the first time as early representatives of Ctenomyinae (Octodontidae), Octodontinae or Abrocomidae. Based on our results, we estimate the divergence of octodontoid families and subfamilies to have occurred during the Late Oligocene, which is consistent with molecular estimates, but older than previous inferences based on the fossil record. Contrary to previous suggestions, we show the first appearances of modern members of Abrocomidae, Octodontinae and Ctenomyinae to be distinctly decoupled from the origin of these clades, with different stages in the evolutionary history of octodontoids seemingly following distinct phases of palaeoenvironmental change. Depending on the phylogenetic pattern, fossils from the stage of differentiation bear evolutionary information that may not be provided by crown groups, thus highlighting the unique and important contribution of fossils to our understanding of macroevolutionary patterns.Facultad de Ciencias Naturales y Muse

Phylogenetic affinities of the late Miocene echimyid †Pampamys and the age of Thrichomys (Rodentia, Hystricognathi)

Phylogenetic affinities of the late Miocene echimyid †Pampamys emmonsae Verzi, Vucetich, and Montalvo, 1995 (Huayquerian South American Land Mammal Age, central Argentina), were analyzed. In the most-parsimonious tree obtained, subfamilies of Echimyidae were nonmonophyletic (except for Dactylomyinae). Two major clades were recovered. One of them included the living fossorial Eumysopinae and the extinct †Theridomysops.The other clade grouped the terrestrial eumysopines Thrichomys (punaré) and Proechimys-Trinomys (spiny rats), and the arboreal eumysopines Mesomys (spiny tree-rats) + Echimyinae - Dactylomyinae. †Pampamys was the sister genus of Thrichomys, suggesting the Huayquerian South American Land Mammal Age (>6.0 million years ago [mya] by biochronology) as a minimum age for the origin of the living genus. Both major echimyid clades recognized here are represented by simplified-molared species in the Huayquerian South American Land Mammal Age. This would be related to the expansion of open environments during the late Miocene, and the geographical bias of the fossiliferous Huayquerian deposits exposed mostly in southern South America.Facultad de Ciencias Naturales y Muse

Phylogenetic affinities of the late Miocene echimyid †Pampamys and the age of Thrichomys (Rodentia, Hystricognathi)

Phylogenetic affinities of the late Miocene echimyid †Pampamys emmonsae Verzi, Vucetich, and Montalvo, 1995 (Huayquerian South American Land Mammal Age, central Argentina), were analyzed. In the most-parsimonious tree obtained, subfamilies of Echimyidae were nonmonophyletic (except for Dactylomyinae). Two major clades were recovered. One of them included the living fossorial Eumysopinae and the extinct †Theridomysops.The other clade grouped the terrestrial eumysopines Thrichomys (punaré) and Proechimys-Trinomys (spiny rats), and the arboreal eumysopines Mesomys (spiny tree-rats) + Echimyinae - Dactylomyinae. †Pampamys was the sister genus of Thrichomys, suggesting the Huayquerian South American Land Mammal Age (>6.0 million years ago [mya] by biochronology) as a minimum age for the origin of the living genus. Both major echimyid clades recognized here are represented by simplified-molared species in the Huayquerian South American Land Mammal Age. This would be related to the expansion of open environments during the late Miocene, and the geographical bias of the fossiliferous Huayquerian deposits exposed mostly in southern South America.Facultad de Ciencias Naturales y Muse

Ontogenetic trajectories of key morphofunctional cranial traits in South American subterranean ctenomyid rodents

Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed in 5 species of the South American subterranean rodent Ctenomys (tuco-tucos). With the exception of upper incisor procumbency, variables showed high correlation with overall skull size. In particular, craniomandibular variables related to the production of bite forces at the incisors showed near-geometric similarity during postnatal growth and interspecific changes in early developmental stages resulting in different starting forms (lateral transposition). Such an interspecific pattern of change is similar to one previously reported to occur among living and extinct ctenomyid genera. These results suggest more evolutionary flexibility for changes in early ontogenetic stages and allow rejection of the hypothesis that interspecific shape differences in the skull of Ctenomys would be associated with differences in size alone.Facultad de Ciencias Naturales y Muse

Colección de mastozoología del Museo de La Plata

La colección de Mastozoología del Museo de La Plata (Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata) comenzó formando parte de un repositorio más amplio que incluía ejemplares de invertebrados y vertebrados vivientes, en el ámbito del Departamento Zoología, cuyo primer jefe fue Fernando Lahille (Torres, 1927). En este contexto, los primeros materiales de mamíferos, correspondientes a esqueletos, se ingresaron en 1908. A partir de 1936 se inició la catalogación independiente de los mamíferos (Frengüelli, 1937: 38), esencialmente de materiales obtenidos mediante donación o colecta a partir de principios del siglo XX. Es una de las colecciones más ricas del país en número de ejemplares (cerca de 6000), y es la segunda más antigua. Está integrada por pieles, cráneos, esqueletos, y en menor proporción materiales conservados en fluidos. Parte de los esqueletos y ejemplares taxidermizados se exponen en cuatro salas de exhibición del Museo (salas XIV, XV, XVI y XVII).Eje 1: Manejo de Colecciones y GestiónRed de Museos de la Universidad Nacional de La Plat

Late Pleistocene echimyid rodents (Rodentia, Hystricognathi) from northern Brazil

Echimyidae (spiny rats, tree rats and the coypu) is the most diverse family of extant South American hystricognath rodents (caviomorphs). Today, they live in tropical forests (Amazonian, coastal and Andean forests), occasionally in more open xeric habitats in the Cerrado and Caatinga of northern South America, and open areas across the southern portion of the continent (Myocastor). The Quaternary fossil record of this family remains poorly studied. Here, we describe the fossil echimyids found in karst deposits from southern Tocantins, northern Brazil. The analyzed specimens are assigned to Thrichomys sp., Makalata cf. didelphoides and Proechimys sp. This is the first time that a fossil of Makalata is reported. The Pleistocene record of echimyids from this area is represented by fragmentary remains, which hinders their determination at specific levels. The data reported here contributes to the understanding of the ancient diversity of rodents of this region, evidenced until now in other groups, such as the artiodactyls, cingulates, carnivores, marsupials, and squamate reptiles.Facultad de Ciencias Naturales y Muse

Phylogenetic affinities of the late Miocene echimyid †Pampamys and the age of Thrichomys (Rodentia, Hystricognathi)

Phylogenetic affinities of the late Miocene echimyid †Pampamys emmonsae Verzi, Vucetich, and Montalvo, 1995 (Huayquerian South American Land Mammal Age, central Argentina), were analyzed. In the most-parsimonious tree obtained, subfamilies of Echimyidae were nonmonophyletic (except for Dactylomyinae). Two major clades were recovered. One of them included the living fossorial Eumysopinae and the extinct †Theridomysops.The other clade grouped the terrestrial eumysopines Thrichomys (punaré) and Proechimys-Trinomys (spiny rats), and the arboreal eumysopines Mesomys (spiny tree-rats) + Echimyinae - Dactylomyinae. †Pampamys was the sister genus of Thrichomys, suggesting the Huayquerian South American Land Mammal Age (>6.0 million years ago [mya] by biochronology) as a minimum age for the origin of the living genus. Both major echimyid clades recognized here are represented by simplified-molared species in the Huayquerian South American Land Mammal Age. This would be related to the expansion of open environments during the late Miocene, and the geographical bias of the fossiliferous Huayquerian deposits exposed mostly in southern South America.Facultad de Ciencias Naturales y Muse

Colección de mastozoología del Museo de La Plata

Fil: Olivares, Adriana Itatí. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Merino, Mariano Lisandro. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Ruperto, Emmanuel. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Verzi, Diego Héctor. Sección Mastozoología. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin