Ontogeny of the skull of Sternotherus odoratus.

97 p. : ill. ; 26 cm. "Issued December 9, 2009." Includes bibliographical references (p. 75-81).There are few published data addressing the types, levels, and patterns of intraspecific variation in gross anatomical structures for nonavian reptiles, especially considering the widespread interest in their morphology and evolutionary history. This study examines variation in both discrete and continuous characters of the postnatal skull for a single population of the kinosternid turtle Sternotherus odoratus. The primary purpose of the study was to elucidate those features that exhibit transformations (and by default those that do not) in the latter two-thirds of postnatal ontogeny--that portion heavily relied upon in phylogenetic analyses of macroanatomical features and most often preserved in the vertebrate fossil record. Data are presented for cranial characters historically used to elucidate phylogenetic relationships in turtles and to assess fossil specimens taxonomically. Results indicate that the number of characters exhibiting postnatal variation, and the levels at which they vary, are surprisingly high considering the conservative nature of both the taxonomic sample and the pool of examined characters. Features associated with the feeding apparatus are among the most variable cranial structures--for both continuous and discrete characters. A relatively large number of discrete transformations occur in structures derived from those cranial elements preformed in cartilage. This concentration demonstrates that developmental trajectories apomorphic for deep nodes in vertebrate phylogenetic history result in relatively late-stage postnatal transformations and high levels of variation in characters informative at much more restricted taxonomic levels. This study provides a baseline of data that future studies examining the ontogenetic and evolutionary history of variation can build upon and it represents a necessary step in understanding the complex system by which variability in developmental modules becomes integrated in the reptile skull

Variation, variability, and the origin of the avian endocranium:Insights from the anatomy of alioramus altai (theropoda: Tyrannosauroidea)

The internal braincase anatomy of the holotype of Alioramus altai, a relatively small-bodied tyrannosauroid from the Late Cretaceous of Mongolia, was studied using high-resolution computed tomography. A number of derived characters strengthen the diagnosis of this taxon as both a tyrannosauroid and a unique, new species (e.g., endocranial position of the gasserian ganglion, internal ramification of the facial nerve). Also present are features intermediate between the basal theropod and avialan conditions that optimize as the ancestral condition for Coelurosauria--a diverse group of derived theropods that includes modern birds. The expression of several primitive theropod features as derived character states within Tyrannosauroidea establishes previously unrecognized evolutionary complexity and morphological plasticity at the base of Coelurosauria. It also demonstrates the critical role heterochrony may have played in driving patterns of endocranial variability within the group and potentially reveals stages in the evolution of neuroanatomical development that could not be inferred based solely on developmental observations of the major archosaurian crown clades. We discuss the integration of paleontology with variability studies, especially as applied to the nature of morphological transformations along the phylogenetically long branches that tend to separate the crown clades of major vertebrate groups

Fig. 17 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 17. Photographs and line drawings of the palatal surface of M-2989 (A) and M-2958 (B). The paired foramina praepalatinum are exposed ventrally in M-2989, whereas they are concealed by caudal development of the premaxillae on the secondary palate in M-2958. Ventral exposure of these foramina is the most common condition within the SMRS.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 20 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 20. Photographs and line drawings of the caudal margin of the left orbital floor and rostral margin of the cavum cranii as viewed through the left orbit of M-2966. A rostral opening of the vidian canal (acnv) lies in the caudal margin of the foramen palatinum posterior. The foramen arteriae anteriovidianae (faa) is a second rostral opening of a vidian canal that transmits a branch of the vidian nerve and vein onto the dorsal surface of the palate.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 24 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 24. Photographs and line drawings of the dorsal surface of the pterygoid in M-2960 (A, left), the rostral end of the pterygoid in M-2982 (B, left), and lateral view of the rostral half of the pterygoid in M- 2960 (C, left). A fossa lying just rostral to the foramen caroticum laterale houses foramina involved in the transmission of the vidian nerve and vein. The anterior canalis nervi vidiani (acnv) transmits the vidian nerve and vein rostrally through the crista pterygoidea before it eventually bifurcates sending branches of the vidian onto the dorsal and ventral surfaces of the palate. Arrows mark the path of the vidian nerve through the foramen pro ramo nervi vidiani (A) and the anterior canalis nervi vidiani (C).Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 30 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 30. Photographs and line drawings of the occipital and basicranial regions in M-2980 (A) and M- 2983 (B) (the least and most mature specimens in the SMRS). Note the relative ossification of the exoccipitals. IX? (B) marks the possible path of the glossopharyngeal nerve out of the recessus scalae tympani, which is delimited by small, processlike ossifications around the rim of the fenestra postotica.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 1 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 1. Phylogenetic hypotheses regarding the systematic position of Sternotherus odoratus. The sister taxon to Kinosternoidea within Cryptodira is currently a point of contention (Meylan and Gaffney, 1989; Krenz et al., 2005; Near et al., 2005). Kinosternoidea here is considered to reflect the crown-clade of Kinosternidae + Dermatemys. This usage follows Joyce et al. (2004) and reflects the unresolved position of Emarginachelys (Shaffer et al., 1997). Asterisks (*) denote extinct lineages.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 28 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 28. Photographs and line drawings of the left basicranial region in posterolateral view through the fenestra postotica in M-2983 (A) and M-2995 (B). Note the increased ossification in M-2983 (a large, mature male) relative to M-2995 (an immature male). This increased ossification is especially apparent around the fenestra ovalis (fo) and the lateral margin of the foramen jugular posterius (fjp). The columella auris is absent in both specimens.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 18 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 18. Photographs and line drawings of the palatal surface of M-2979 (A), M-2974 (B), and M-2983 (C). The palatines obscure the vomer-pterygoid contact in M-2974. The shape of the vomer-pterygoid contact can be broadly rounded or obtuse as in M-2974 or the vomer can terminate caudally at a single point as in M-2983. The development of the rostral margin of pterygoid appears to be the major factor controlling the morphology of this character.Published as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt

Fig. 34 in Postnatal Ontogeny Of The Skull In Th E Ex Tant North Am Eric An Turtle Sternotherus Odoratus (Crypto Dir A: Kinosterni Dae) G A B E S. B E V Er

Fig. 34. Plots of principal components scores derived from 25 continuous characters for Sternotherus odoratus from the SMRS. Plots A and B represent scores based on 25 continuous characters from the skull and lower jaws. Plot C represent principal component scores derived from 20 continuous characters from the skull only. CirclesPublished as part of <i>Bever, Gabe S., 2009, Bulletin of the American Museum of Natural History (London, England) 2009 (330)</i> on pages 1-97, DOI: 10.1206/330.1, <a href="http://zenodo.org/record/10111568">http://zenodo.org/record/10111568</a&gt