Abstract View

Naish D, Simpson M, Dyke G (2013) A New Small-Bodied Azhdarchoid Pterosaur from the Lower Cretaceous of England and Its Implications for Pterosaur Anatomy, Diversity and Phylogeny. PLoS ONE 8(3): e58451. doi:10.1371/journal.pone.0058451
Background
Pterosaurs have been known from the Cretaceous sediments of the Isle of Wight (southern England, United Kingdom) since 1870. We describe the three-dimensional pelvic girdle and associated vertebrae of a small near-adult pterodactyloid from the Atherfield Clay Formation (lower Aptian, Lower Cretaceous). Despite acknowledged variation in the pterosaur pelvis, previous studies have not adequately sampled or incorporated pelvic characters into phylogenetic analyses.
Methodology/Principal Findings
The new specimen represents the new taxon Vectidraco daisymorrisae gen. et sp. nov., diagnosed by the presence of a concavity posterodorsal to the acetabulum and the form of its postacetabular process on the ilium. Several characters suggest that Vectidraco belongs to Azhdarchoidea. We constructed a pelvis-only phylogenetic analysis to test whether the pterosaur pelvis carries a useful phylogenetic signal. Resolution in recovered trees was poor, but they approximately matched trees recovered from analyses of total evidence. We also added Vectidraco and our pelvic characters to an existing total-evidence matrix for pterosaurs. Both analyses recovered Vectidraco within Azhdarchoidea.
Conclusions/Significance
The Lower Cretaceous strata of western Europe have yielded members of several pterosaur lineages, but Aptian pterosaurs from western Europe are rare. With a pelvis length of 40 mm, the new animal would have had a total length of c. 350 mm, and a wingspan of c. 750 mm. Barremian and Aptian pterodactyloids from western Europe show that small-bodied azhdarchoids lived alongside ornithocheirids and istiodactylids. This assemblage is similar in terms of which lineages are represented to the coeval beds of Liaoning, China; however, the number of species and specimens present at Liaoning is much higher. While the general phylogenetic composition of western European and Chinese communities appear to have been approximately similar, the differences may be due to different palaeoenvironmental and depositional settings. The western Europe pterodactyloid record may therefore be artificially low in diversity due to preservational factors.

A New Species of Auk (Charadriiformes, Pan-Alcidae) from the Miocene of Mexico
N. Adam Smith
The Condor 2013 115 (1), 77-83

A fossil from the Middle Miocene Rosarito Beach Formation of Baja California represents a previously undescribed, auklet-sized species of wing-propelled diving Pan-Alcidae (Aves, Charadriiformes). This new taxon, Divisulcus demerei, is recognized from the presence of a bifurcated scapulotricipital sulcus of the distal end of the humerus, a potentially neomorphic character within Aves. Additionally, the degree of compression of the humeral shaft of this new species is less than that of other pan-alcids. These characters may represent retention of ancestral character states that are associated with the transition to wing-propelled diving from nondiving Charadriiformes. This discovery provides further information regarding paleodiversity in this clade, extends the geographic range of Miocene pan-alcids, and may represent the oldest record of the clade from the Pacific Ocean basin, as previously reported unambiguous records are from Late Miocene or younger deposits (10–1.6 Ma). Moreover, the age of this new pan-alcid (14–16 Ma) corresponds with the timing of the Middle Miocene climatic optimum, a time for which previous records of Pacific Ocean basin pan-alcids were lacking. Because of the relative incompleteness of the specimen, the systematic position of this new taxon within the Pan-Alcidae from a phylogenetic analysis is not strongly supported. Until additional remains of D. demerei are recovered that can provide additional character data, the affinities of this new taxon within the Pan-Alcidae are uncertain.

Pliocene Giraffidae (Mammalia) from the Hadar Formation of Hadar and Ledi-Geraru, Lower Awash, Ethiopia
Denis Geraads, Kaye Reed, and Rene Bobe
Journal of Vertebrate Paleontology 2013 33 (2), 470-481

The Hadar giraffids belong to the genera Giraffa and Sivatherium. We recognize two species in the former genus; distinguishing between them on dental elements is straightforward, but it is more difficult on other remains. Giraffa jumae is about the size of the modern G. camelopardalis, but has a less pneumatized skull with more conical ossicones, more slender and often longer limb bones, and also differs in some dental features, making it an unlikely ancestor of the modern giraffe. Giraffa stillei has teeth that are always smaller than those of the modern form, less molarized premolars, ossicones smaller but otherwise similar to those of the larger Hadar species, and slender limb bones that are probably relatively long, thus not much shorter than those of the modern form. It might be the ancestor of the later G. gracilis from the Turkana Basin, and of G. camelopardalis. We assign no specimen to Giraffa pygmaea. Sivatherium maurusium, a well-known form of the African Pliocene and Pleistocene, is a rare form at Hadar. In contrast to most bovids, giraffids are more common in the Sidi Hakoma than in the overlying Denen Dora Member, perhaps as a result of grassland expansion at Hadar at that time.

External and Internal Anatomy of a Petrosal from the Late Paleocene of Itaboraí, Brazil, Referred to Notoungulata (Placentalia)
Guillaume Billet and Christian De Muizon
Journal of Vertebrate Paleontology 2013 33 (2), 455-469

We describe the earliest petrosal bone referred to the South American endemic Notoungulata, from the late Paleocene-early Eocene Beds of Itaboraí, which provides a critical basis for assessing their enigmatic origins. As indicated by our phylogenetic analysis, the fossil belongs to a taxon most likely close to the ancestral root of the Notoungulata. We describe the entire external anatomy of this isolated ear bone and also investigate the bony labyrinth of the inner ear through computed tomographic scan reconstruction. Within Notoungulata, the specimen retains a number of features considered plesiomorphic, such as a narrow medial flange on the tympanic surface, the presence of a petromastoid canal, and a rather deep fossa subarcuata. We also present a survey of the petrosal anatomy of early diverging notoungulates compared with other members of Eutheria. Features regarded as plesiomorphic in Notoungulata comprise a low stapedial ratio, a cavity for the trigeminal ganglion, a secondary crus commune, a ramus superior of stapedial artery (although reduced) and arteria diploëtica magna, and the tegmen tympani pierced by a canal. Derived features include notably a laterally located tensor tympani fossa, a bean-shaped promontorium and adjoining flattened medial flange, and a stapedial fossa poorly separated from the postpromontorial tympanic sinus. A number of derived notoungulate characters are interestingly shared with the extant hyrax Procavia. Further investigation of this anatomical region in other eutherians is required in order to fully exploit the phylogenetic potential of our new observations. This is especially needed for other groups of South American endemic ungulates possibly related to Notoungulata.

The Earliest Known Fisher (Mustelidae), a New Species from the Rattlesnake Formation of Oregon
Joshua X. Samuels and Jennifer Cavin
Journal of Vertebrate Paleontology 2013 33 (2), 448-454

Fishers are elusive carnivorans, with few occurrences in the fossil record. The origin and early evolution of fishers is unclear, but they likely originated in Asia. A new record of Pekania from the Rattlesnake Formation of Oregon represents the earliest known occurrence of a fisher, more than 5 million years earlier than other records in North America. This specimen has an unambiguous derived trait shared with other members of the genus, an external median rootlet on the upper carnassial The age of this new find is inferred to be between 7.05 and 7.3 Ma, through radiometric and magnetostratigraphic dating. This age is supported by the presence of specimens of a shrew, Sorex edwardsi, and a rhinoceros, cf. Teleoceras, found at the same locality, as well as a rabbit, Hypolagus cf. vetus, and a tapir nearby, all of which are well known from early Hemphillian deposits. This find indicates that fishers were in both North America and Asia in the late Miocene, around the time of their divergence from other members of the clade as estimated from genetic data. Although it is over 7 million years old, this species shows remarkable similarity to extant P. pennanti, highlighting the highly conservative nature of gulonine mustelids. The Rattlesnake specimen is more robust than other fisher species, possibly representing something close to the ancestry of all fishers.

Systematics and Biogeography of Crocodylians from the Miocene of Panama
Alexander K. Hastings, Jonathan I. Bloch, Carlos A. Jaramillo, Aldo F. Rincon, and Bruce J. MacFadden
Journal of Vertebrate Paleontology 2013 33 (2), 239-263

Despite the fact that fossil crocodylians have been recovered from the Panama Canal Zone starting with initial excavations in 1912, detailed studies have been lacking. Recent excavations of the canal have resulted in new discoveries of many vertebrate fossils, including the first known Miocene crocodylian skulls from Central America. These fossil skulls from the early-middle Miocene represent two new taxa with distinct morphology that is shared with extinct and extant caimans (Caimaninae). A cladistic analysis of 32 alligatorid and three outgroup taxa, scored for 75 characters, resulted in 1210 equally most parsimonious cladograms, all of which suggest that Culebrasuchus mesoamericanus, gen. et sp. nov., is the sister taxon to all previously known Caimaninae. Additionally, the analysis suggests that Centenariosuchus gilmorei, gen. et sp. nov., is the sister taxon to a caimanine clade that includes Purussaurus from the Miocene of South America. In fact, teeth very similar to those of Purussaurus have also been recovered from the Panama Canal. Given these South American affinities, we suggest that these early caimanines dispersed across saltwater. This is a potentially surprising result, because all extant alligatorids lack the salt glands that would have been necessary for the marine dispersal required to reach Central America during the Miocene. Unlike Miocene mammals that all have North American affinities, the Miocene crocodylians of Panama represent a ‘melting pot’ with taxa of disparate origins living together at the southern extreme of Central America.

Cats in the forest: predicting habitat adaptations from humerus morphometry in extant and fossil Felidae (Carnivora)

Carlo Meloro, Sarah Elton, Julien Louys, Laura C. Bishop, Peter Ditchfield
Paleobiology 2013 39 (3), 323-344

We found no significant differences in the predictive power of distinct morphometric descriptors or habitat criteria, although sample splitting into small and large cat guilds greatly improves the stability of the models. Significant insights emerge for three long-canine cats: Smilodon populator, Paramachairodus orientalis, and Dinofelis sp. from Olduvai Gorge (East Africa). S. populator and P. orientalis are both predicted to have been closed-habitat adapted taxa. The false “sabertooth” Dinofelis sp. from Olduvai Gorge is predicted to be adapted to mixed habitat. The application of felid humerus ecomorphology to the carnivoran record of Olduvai Gorge shows that the older stratigraphic levels (Bed I, 1.99–1.79 Ma) included a broader range of environments than Beds II or V, where there is an abundance of cats adapted to open environments.

A New Giant Salamander (Urodela, Pancryptobrancha) from the Miocene of Eastern Europe (Grytsiv, Ukraine)
Davit Vasilyan, Madelaine Böhme, Viacheslav M. Chkhikvadze, Yuriy A. Semenov, and Walter G. Joyce
Journal of Vertebrate Paleontology 2013 33 (2), 301-318

We present new and well-preserved giant salamander material from the Miocene of the Grytsiv locality, Ukraine. Disarticulated skull and postcranial bones from two individuals are described as a new taxon, Ukrainurus hypsognathus, gen. et sp. nov. U. hypsognathus is characterized by poorly ossified bone tissues, relatively inflexible mandibles, a high dentary, a crista on the lingual surface of the dentary, a pars dentalis of the dentary that is composed of a dental lamina and a subdental surface, presence of an eminentia dorsalis on the squamosal, a broad pericondylar facet on the occipital, extremely elongated prezygapophyses, and hemal processes with an elongate, oval base. Moreover, U. hypsognathus shows evidence of strong mandibular levator muscles that indicate great biting force. A phylogenetic analysis of all well-understood Tertiary and Recent giant salamanders recovers a monophyletic group of Asian and North American cryptobranchids, but places U. hypsognathus outside crown group Cryptobranchidae. This result suggests that Cryptobranchidae originated in Asia and dispersed to North America. The oldest representative of crown Cryptobranchidae is Aviturus exsecratus from the terminal Paleocene of the Nemegt Basin, Mongolia.

Redescription of Dasypus punctatus Lund, 1840 and Considerations on the Genus Propraopus Ameghino, 1881 (Xenarthra, Cingulata)
Mariela C. Castro, Ana Maria Ribeiro, Jorge Ferigolo, and Max C. Langer
Journal of Vertebrate Paleontology 2013 33 (2), 434-447

The comparative description of the most complete specimen of Dasypus punctatus (Xenarthra, Cingulata), from southeastern Brazil, reveals that the species differs from other Dasypodini by the numerous foramina it has in both buckler and movable osteoderms, providing the basis for the lectotype designation. This species was historically allocated to Propraopus, but the inclusiveness and monophyly of that genus are uncertain. A new phylogenetic analysis groups D. punctatus with the living species of Dasypus in a monophyletic clade for the genus, also supporting a Propraopus clade composed of P. sulcatus and the type species P. grandis. The palatal anatomy corroborates previously suggested affinities between D. kappleri and D. punctatus. On the contrary, the possible synonymy between P. grandis and P. sulcatus needs further investigation, given that they differed on a single character. As usual in cingulate systematics, characters related to osteoderm ornamentation proved essential to determine the relationships of taxa. However, their use requires careful sampling in order to account for intraspecific variation biases.

First Central American Record of Anthracotheriidae (Mammalia, Bothriodontinae) from the Early Miocene of Panama
Aldo F. Rincon, Jonathan I. Bloch, Bruce J. MacFadden, and Carlos A. Jaramillo
Journal of Vertebrate Paleontology 2013 33 (2), 421-433

A new species of bothriodontine anthracothere, Arretotherium meridionale, is described from the early Miocene (Arikareean North America Land Mammal Age) Las Cascadas fossil assemblage in Panama, Central America. Fossils of A. meridionale are the first record of an anthracothere from the New World Tropics. Among anthracotheres, A. meridionale is most similar to A. acridens from the middle Arikareean from Texas in having a relatively deep and robust jaw, high and sharp cusps on the lower molars, short c—p1 diastema, and absence of a mesiolingual metacristid. A. meridionale differs from other species in being generally larger, two lower incisors (rather than three), prehypocristid never reaching the postprotocristid, more apical junction between postprotocristid and postmetacristid, mesiolingual entocristid transversely notching preentocrisitid, and transverse valley tapered lingually by prehypocristid. Although cladistic analysis of 28 anthracotheriids coded for 51 characters supports a relationship between A. meridionale and A. acridens, some presumably convergent dental characteristics are also similar to certain Oligocene-Miocene Eurasian bothriodontines. The presence of Arretotherium in the Las Cascadas Formation in Panama, and absence in the later Centenario Fauna, shows that primitive bothriodontines entered into Central America by the early Miocene before disappearing from the New World during the late early-middle Miocene.

A Reevaluation of the Harrodsburg Crevice Fauna (Late Pleistocene of Indiana, U.S.A.) and the Climatic Implications of Its Mammals
Michael R. Smith and P. David Polly
Journal of Vertebrate Paleontology 2013 33 (2), 410-420

The mammal fauna from Harrodsburg Crevice, a late Pleistocene site from southern Indiana, U.S.A., has several notable features, including one of the most northerly occurrences of Panthera onca augusta (Pleistocene jaguar) and a putatively late occurrence of Platygonus vetus (Pleistocene American peccary). The fauna contains 1050 specimens distributed among 21 identifiable species, including members of Canidae, Felidae, Mephitidae, Equidae, Tayassuidae, Talpidae, Geomyidae, Scuiridae, and Cricetidae. Two previously published radiocarbon dates (25,050 and 34,460 years before present [ybp]) suggested that the Harrodsburg fauna belonged to an interstadial of the Wisconsinan (marine isotope stage [MIS] 2 or 3), which if true would make the occurrence of P. onca the northernmost of the Rancholabrean and the occurrence of P. vetus the only one in the Rancholabrean. Based on biostratigraphic and environmental analysis of the mammals, we argue that the Harrodsburg fauna is older, likely from the last full interglacial period (Sangamonian, MIS 5e, approximately 125 ka). Cluster analysis failed to link the Harrodsburg fauna with any nearby late Pleistocene to Recent sites and more closely linked it to sites in south-central Texas. Areas of maximum sympatry suggest that the paleoclimate of the Harrodsburg fauna had mean annual temperatures of 12.5–14.5°C, similar to modern Arkansas and Kentucky. Paleoclimate models suggest that the nearest areas with that climate during the last glacial maximum (18–20 ka) were in northern Florida or Texas, whereas the appropriate climate was found in the Harrodsburg area during the last interglacial. Attempts to replicate the published radiocarbon dates failed because collagen in the fossil material is degraded, leading us to conclude that the published dates are unlikely to represent the true age of the material.

What Constitutes a Fossil Mammal Community in the Early Miocene Santa Cruz Formation?
Darin A. Croft
Journal of Vertebrate Paleontology 2013 33 (2), 401-409

The late early Miocene Santa Cruz Formation of southern Argentina is one of the most productive fossil mammal-bearing formations in South America. Hundreds of species have been named from this formation, resulting in a clear overestimation of Santa Cruz mammal diversity. Recent paleoecological studies have attempted to minimize this problem by analyzing more restricted faunal lists based only on recently collected fossil samples. In some cases, this approach has excluded clearly recognizable Santa Cruz taxa. In this study, I use a family-level rarefaction analysis of the Yale Peabody Collection of Santa Cruz fossils to test whether such absences are likely due to smaller sample size or to other factors. I further attempt to reconcile these absences using distributional data from recent and historical Santa Cruz Formation collections. The rarefaction analysis indicates that most single-locality samples from the Santa Cruz Formation have lower familial diversity than expected based on the taxonomic distribution of specimens in the Princeton University Collection at Yale Peabody Museum (YPM-PU) as a whole. However, I conclude that single-locality samples are not necessarily more appropriate than multi-locality samples for paleoecological analyses of ancient Santa Cruz Formation mammal communities given the large regional extent of the Santa Cruz Formation and the large geographic area encompassed by most modern communities used for comparison. This study highlights the need for more precise stratigraphic correlations among Santa Cruz localities and integration of important historical collections into a modern stratigraphic framework.

A New Species of Threskiornithidae-Like Bird (Aves, Ciconiiformes) from the Green River Formation (Eocene) of Wyoming
Nathan D. Smith, Lance Grande, and Julia A. Clarke
Journal of Vertebrate Paleontology 2013 33 (2), 363-381

A new avian species from the late early Eocene Fossil Butte Member of the Green River Formation is described based on a nearly complete postcranial skeleton. The new species, Vadaravis brownae, gen. et sp. nov., can be diagnosed by a unique combination of characters, including the following autapomorphies, which are unique among Aves: two (cranial and caudal) small and discrete pneumatopores on the lateral sides of the caudal-most thoracic centra; and a caudoventrally located pisiform process of the carpometacarpus that projects only weakly cranially. Phylogenetic analyses recover Vadaravis as a member of the waterbird assemblage (including, e.g., penguins, storks, pelicans), closely related to taxa traditionally placed within the avian order Ciconiiformes (storks, flamingos, herons, the hamerkop, ibises, and spoonbills). Additional morphological features and a phylogenetic analysis constrained by a recently recovered waterbird topology suggest close affinities between Vadaravis and Threskiornithidae. This new species represents the first proposed part of Ciconiiformes (and possibly stem-Threskiornithidae) in the Green River Formation of North America. Its discovery increases the known taxonomic and ecological diversity of this diverse fossil avifauna. Vadaravis also represents one of the oldest members of Ciconiiformes (and possibly stem-Threskiornithidae), and implies that additional lineages within the waterbird assemblage had diverged by the late early Eocene.

A New Juvenile Specimen of Guanlingsaurus (Ichthyosauria, Shastasauridae) from the Upper Triassic of Southwestern China
Cheng Ji, Da-Yong Jiang, Ryosuke Motani, Wei-Cheng Hao, Zuo-Yu Sun, and Tao Cai
Journal of Vertebrate Paleontology 2013 33 (2), 340-348

A new nearly complete skeleton from the Wayao Member of the Falang Formation (lower Carnian, Upper Triassic) of Guizhou, South China, is described and ascribed as a juvenile individual of Guanlingsaurus liangae. The new specimen supplies hitherto unknown information on this species: a complete pelvic girdle shows that the ilium was misidentified as the ischium by previous authors; complete hyoids show that their length was overestimated previously; unlike in other shastasaurids, the obturator foramen on the pubis is widely open as part of the obturator fossa; and the fibula has a posterior flange, similar to that of Shonisaurus. Guanlingsaurus liangae was reassigned to the genus Shastasaurus and was suggested to be a suction feeder due to its short snout, lack of teeth, and hyoid. However, the new specimen of Guanlingsaurus described here shows much smaller hyoids compared with Shonisaurus, which was thought to be a suction-feeding ichthyosaur. Suction feeding in ichthyopterygians as a whole requires scrutiny: the group lacks an ossified hyoid corpus that is typically expanded in suction-feeding cetaceans, which suggests that ichthyopterygian hyoids were insufficiently robust for suction feeding. A phylogenetic analysis of Ichthyopterygia based on a revised data matrix clarifies the shastasaurid affinity of G. liangae as a sister taxon of Shonisaurus, with Shastasaurus as their sister group, and Shonisaurus is reestablished as a genus containing Shonisaurus sikanniensis as traditionally held. It suggests that the assignment of Guanlingsaurus and Shonisaurus sikanniensis to Shastasaurus unnecessarily confuses existing taxonomy.

New Material of the Choristodere Lazarussuchus (Diapsida, Choristodera) from the Paleocene of France
Ryoko Matsumoto, Eric Buffetaut, Francois Escuillie, Sophie Hervet, and Susan E. Evans
Journal of Vertebrate Paleontology 2013 33 (2), 319-339

Choristodera is a clade of freshwater aquatic reptiles with a strictly Laurasian distribution and a temporal record extending from at least Middle Jurassic to Miocene. The large Cretaceous-Eocene neochoristoderes Champsosaurus and Simoedosaurus are the most familiar taxa, but many smaller representatives have since been recognized. Neochoristoderes disappeared from the fossil record in the Eocene, but choristoderes survived into the European Neogene in the form of the small, superficially lizard-like Lazarussuchus. This taxon was originally described from the late Oligocene of France but has subsequently been recorded from the early Miocene of the Czech Republic and the late Oligocene of Germany. Despite its age, most phylogenetic analyses place Lazarussuchus at or close to the base of the choristoderan tree, implying a very long unrecorded history. A new specimen of Lazarussuchus from the late Paleocene locality of Menat, France, partly fills that hiatus. The genus was thus present in the waterways of western Europe for at least 30 Ma, and was probably considerably more widespread than current records suggest. A new phylogenetic analysis confirms its placement outside Neochoristodera, but the relationships of non-neochoristoderan taxa remain incompletely resolved.

Dieser Beitrag wurde unter Wissenschaft/Naturschutz abgelegt und mit , , , , , , , , , , , , , verschlagwortet. Setze ein Lesezeichen auf den Permalink.

Kommentar verfassen