Detailed anatomy of the braincase ofMacelognathus vagansMarsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny

BackgroundMacelognathus vagansMarsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocodylomorph. However, a partial skull found in association with mandibular and postcranial remains was not described.MethodsDue to the small size and delicate structures within the braincase, micro CT studies were performed on this specimen. The new anatomical information was incorporated in a phylogenetic dataset, expanding both character and taxon sampling.ResultsThis new material reinforces the non-crocodyliform crocodylomorph affinities ofMacelognathusas it bears a large otic aperture, unfused frontals and lacks ornamentation on the dorsal cranial bones. The internal structures also support these affinities as this specimen bears traits (i.e., heavily pneumatized and expanded basisphenoid; the presence of additional pneumatic features on the braincase; and the otoccipital-quadrate contact) not present in most basal crocodylomorphs. Furthermore, the presence of a wide supraoccipital and a cranioquadrate passage are traits shared withAlmadasuchusfrom the early Late Jurassic of Argentina.Macelognathuswas recovered as one of the closest relatives of crocodyliforms, forming a clade (Hallopodidae) with two other Late Jurassic taxa (AlmadasuchusandHallopus).DiscussionThe clade formed byAlmadasuchus+Hallopus+Macelognathus, the Hallopodidae, is characterized by a higher degree of suturing of the braincase, posteriorly closed otic aperture (paralleled in mesoeucrocodylians) and cursorial adaptations. Also, the phylogenetic position of this lineage of derived crocodylomorphs as the sister group of Crocodyliformes implies a large amount of unsampled record (ghost lineage), at least 50 million years.

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New material of the ‘microsaur’ Llistrofus from the cave deposits of Richards Spur, Oklahoma and the paleoecology of the Hapsidopareiidae

PeerJ ◽

10.7717/peerj.6327 ◽

2019 ◽

Vol 7 ◽

pp. e6327 ◽

Cited By ~ 6

Author(s):

Bryan M. Gee ◽

Joseph J. Bevitt ◽

Ulf Garbe ◽

Robert R. Reisz

Keyword(s):

Evolutionary History ◽

Substantial Reduction ◽

Sister Group ◽

Phylogenetic Position ◽

Neutron Tomography ◽

Early Permian ◽

Cave Deposits ◽

Internal Structures ◽

History Of ◽

New Material

The Hapsidopareiidae is a group of “microsaurs” characterized by a substantial reduction of several elements in the cheek region that results in a prominent, enlarged temporal emargination. The clade comprises two markedly similar taxa from the early Permian of Oklahoma, Hapsidopareion lepton and Llistrofus pricei, which have been suggested to be synonymous by past workers. Llistrofus was previously known solely from the holotype found near Richards Spur, which consists of a dorsoventrally compressed skull in which the internal structures are difficult to characterize. Here, we present data from two new specimens of Llistrofus. This includes data collected through the use of neutron tomography, which revealed important new details of the palate and the neurocranium. Important questions within “Microsauria” related to the evolutionary transformations that likely occurred as part of the acquisition of the highly modified recumbirostran morphology for a fossorial ecology justify detailed reexamination of less well-studied taxa, such as Llistrofus. Although this study eliminates all but one of the previous features that differentiated Llistrofus and Hapsidopareion, the new data and redescription identify new features that justify the maintained separation of the two hapsidopareiids. Llistrofus possesses some of the adaptations for a fossorial lifestyle that have been identified in recumbirostrans but with a lesser degree of modification (e.g., reduced neurocranial ossification and mandibular modification). Incorporating the new data for Llistrofus into an existing phylogenetic matrix maintains the Hapsidopareiidae’s (Llistrofus + Hapsidopareion) position as the sister group to Recumbirostra. Given its phylogenetic position, we contextualize Llistrofus within the broader “microsaur” framework. Specifically, we propose that Llistrofus may have been fossorial but was probably incapable of active burrowing in the fashion of recumbirostrans, which had more consolidated and reinforced skulls. Llistrofus may represent an earlier stage in the step-wise acquisition of the derived recumbirostran morphology and paleoecology, furthering our understanding of the evolutionary history of “microsaurs.”

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An ornithurine bird coracoid from the Late Cretaceous of Alberta, Canada

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2019-0202 ◽

2020 ◽

pp. 1-7

Author(s):

Sydney R. Mohr ◽

John H. Acorn ◽

Gregory F. Funston ◽

Philip J. Currie

Keyword(s):

North America ◽

Late Cretaceous ◽

Ct Scans ◽

Micro Ct ◽

Internal Structures ◽

Postcranial Remains ◽

Dinosaur Park Formation ◽

Upper Campanian

The Cretaceous birds of Alberta are poorly known, as skeletal elements are rare and typically consist of fragmentary postcranial remains. A partial avian coracoid from the upper Campanian Dinosaur Park Formation of Alberta, Canada, can be referred to the Ornithurae, and is referred to here as Ornithurine G (cf. Cimolopteryx). Its structure is similar to previously described ornithurine coracoids from Alberta and other localities in North America, particularly those belonging to the genus Cimolopteryx. A comparison of these elements indicates that the new coracoid is distinct; however, its preservation prevents complete diagnosis. As other Cimolopteryx are Maastrichtian in age, Ornithurine G (cf. Cimolopteryx) also represents the earliest occurrence of a Cimolopteryx-like anatomy. A pneumatized coracoid is a diagnostic trait of Neornithes, identified by the presence of a pneumatic foramen. Ornithurine G (cf. Cimolopteryx) does not preserve this feature. CT and micro-CT scans of both pneumatic and apneumatic coracoids of modern birds show similar internal structures to Ornithurine G (cf. Cimolopteryx), indicating that pneumaticity of the coracoid cannot be determined in the absence of an external pneumatic foramen. A comparison between members of Cimolopterygidae, including Cimolopteryx and Lamarqueavis, raises questions about the assignment of Lamarqueavis to the Cimolopterygidae, and the validity of this family as a whole.

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A phylogeny of Plesiosauria (Sauropterygia) and its bearing on the systematic status of Leptocleidus Andrews, 1922

Zootaxa ◽

10.11646/zootaxa.1863.1.1 ◽

2008 ◽

Vol 1863 (1) ◽

pp. 1 ◽

Cited By ~ 74

Author(s):

PATRICK S. DRUCKENMILLER ◽

ANTHONY P. RUSSELL

Keyword(s):

Late Jurassic ◽

Cladistic Analysis ◽

Sister Group ◽

Phylogenetic Position ◽

Sister Group Relationship ◽

New Taxon ◽

Short Neck ◽

Operational Taxonomic Units ◽

Phylogenetic Hypotheses ◽

The Uk

Leptocleidus Andrews, 1922 is a poorly known plesiosaur genus from Lower Cretaceous successions of the UK, South Africa, and Australia. Historically, there has been little consensus regarding its phylogenetic position within Plesiosauria, largely because of its seemingly aberrant combination of a relatively small skull and short neck. As a result, a diverse array of potential sister groups have been posited for Leptocleidus, including long-necked Cretaceous elasmosaurids, Early Jurassic “rhomaleosaurs”, and Middle to Late Jurassic pliosaurids. A cladistic analysis including Leptocleidus, and a new, apparently morphologically similar specimen from Alberta, TMP 94.122.01, was undertaken to assess their phylogenetic position within Plesiosauria. A character-taxon matrix was assembled afresh, consisting of 33 operational taxonomic units sampled broadly among plesiosaurs. 185 cranial and postcranial characters used in plesiosaur phylogenetics were critically reanalyzed, of which 152 were employed in the parsimony analysis. The results indicate a basal dichotomous split into the traditionally recognized pliosauroid and plesiosauroid clades. Nested within Pliosauroidea, a monophyletic Leptocleididae was recovered, consisting of L. superstes Andrews, 1922 and L. capensis (Andrews, 1911a). In contrast to earlier suggestions, Leptocleidus neither clusters with Rhomaleosaurus, which was found to be paraphyletic, nor with large-skulled pliosaurid taxa, such as Simolestes. Rather, a sister group relationship between Cretaceous Polycotylidae and Leptocleididae was recovered, which is here named Leptocleidoidea. Although TMP 94.122.01 is superficially similar to Leptocleidus, several discrete characters of the skull nest this new taxon within Polycotylidae. Compared to other phylogenetic hypotheses of plesiosaurs, these results are more congruent with respect to the stratigraphic distribution of leptocleidoids. A classification for Plesiosauria is presented.

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Phylogenetic position of Aerumnosa Mohrig (Diptera, Sciaridae) as revealed by multigene analysis, with the description of four new Oriental species

Zootaxa ◽

10.11646/zootaxa.4399.2.8 ◽

2018 ◽

Vol 4399 (2) ◽

pp. 248 ◽

Cited By ~ 2

Author(s):

PEKKA VILKAMAA ◽

HANS-GEORG RUDZINSKI ◽

NIKOLA BURDÍKOVÁ ◽

JAN ŠEVČÍK

Keyword(s):

Phylogenetic Analysis ◽

New Species ◽

Papua New Guinea ◽

Sister Group ◽

Phylogenetic Position ◽

Phylogenetic Hypothesis ◽

Gene Markers ◽

Multigene Analysis ◽

Molecular Phylogenetic ◽

New Material

Four Oriental species of Aerumnosa Mohrig, 1999 (Diptera: Sciaridae), a genus previously known only from Papua New Guinea, are newly described and illustrated: Aerumnosa bituberculata sp. n. (India), A. gemmifera sp. n. (Malaysia: Sabah), A. horrifica sp. n. (Brunei, Thailand) and A. impar sp. n. (Malaysia: Sabah). On the basis of the new material, the genus is redefined. A key to the known species of Aerumnosa is presented, including four new species. An updated molecular phylogenetic analysis based on four gene markers (18S, 28S, 16S and COI) shows Aerumnosa to be a member of the subfamily Cratyninae. The monophyly of Cratyninae is well supported, which clade also includes the genera Hyperlasion Schmitz, 1919, Pnyxiopalpus Vilkamaa & Hippa, 1999 and Pseudoaerumnosa Rudzinski, 2006. According to the present phylogenetic hypothesis, the monophyly of Cratyna Winnertz, 1967 s. l. needs to be revisited. The clade including Cratyna (s. str.) ambigua (Lengersdorf, 1934) appears as the sister group of Aerumnosa.

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Revision of Undorosaurus, a mysterious Late Jurassic ichthyosaur of the Boreal Realm

10.31233/osf.io/s95xm ◽

2019 ◽

Author(s):

Nikolay Zverkov

Keyword(s):

New Taxa ◽

Type Species ◽

Late Jurassic ◽

Sister Group ◽

Phylogenetic Position ◽

Posterior Edge ◽

Diagnostic Features ◽

Type Series ◽

Phylogenetic Hypotheses ◽

Boreal Realm

Recent study of ophthalmosaurid ichthyosaurs has brought us a number of new taxa, however, the validity of several ophthalmosaurid taxa from the Volgian (Tithonian) of European Russia still remains unclear, complicating the comparisons and in some cases affecting taxonomic decisions of new contributions. A revision of the type series of all three species of Undorosaurus, erected by Efimov in 1999, reveals the potential validity of two of them. This contradicts previous research, which concluded that only the type species, U. gorodischensis, is valid. Furthermore, examination of the holotype of Cryopterygius kristiansenae from the coeval strata of Svalbard show that it is synonymous with Undorosaurus gorodischensis sharing all diagnostic features of the species, especially those related to forelimb morphology: humerus with extensive anteroposteriorly elongate proximal end, poorly pronounced trochanter dorsalis and reduced deltopectoral crest; and ulna proximodistally elongate and not involved in perichondral ossification on its whole posterior edge. This supports the idea of intensive exchange of ichthyosaurs between the Middle Russian Sea and other Boreal seas in the Late Jurassic. In order to resolve the phylogenetic position of Undorosaurus within Ophthalmosauridae as well as relations of other ophthalmosaurids, a new dataset including 33 taxa and 106 characters, 23 of which are new, was compiled. The results of this analysis challenge all previous phylogenetic hypotheses for Ophthalmosauridae in a number of aspects including Undorosaurus spp. recovered deeply nested within Platypterygiinae as a sister group to derived platypterygiines.

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The phylogenetic position of the Tyrannosauridae: implications for theropod systematics

Journal of Paleontology ◽

10.1017/s0022336000026706 ◽

1994 ◽

Vol 68 (5) ◽

pp. 1100-1117 ◽

Cited By ~ 185

Author(s):

Thomas R. Holtz

Keyword(s):

Early Cretaceous ◽

Late Cretaceous ◽

Adaptive Radiation ◽

Late Jurassic ◽

Cladistic Analysis ◽

Sister Group ◽

The Other ◽

Phylogenetic Position ◽

African Form ◽

Large Predators

Tyrannosaurids are a well-supported clade of very large predatory dinosaurs of Late Cretaceous Asiamerica. Traditional dinosaurian systematics place these animals within the infraorder Carnosauria with the other large theropods (allosaurids, megalosaurids). A new cladistic analysis indicates that the tyrannosaurs were in fact derived members of the Coelurosauria, a group of otherwise small theropods. Despite certain gross cranial similarities with the large predators of the Jurassic and Early Cretaceous, the Late Cretaceous tyrannosaurids are shown to be the sister group to ornithomimids and troodontids, which share a derived condition of the metatarsus. This clade is found to be nested within Maniraptora, which is a more inclusive taxon than previously recognized. The atrophied carpal structure found in tyrannosaurids and ornithomimids is derived from a maniraptoran condition with a large semilunate carpal, rather than from the plesiomorphic theropod morphology.The taxa “Carnosauria” and “Deinonychosauria” (Dromaeosauridae plus Troodontidae) are shown to be polyphyletic, and the Late Jurassic African form Elaphrosaurus is found to be the sister taxon to Abelisauridae rather than a primitive ornithomimosaur. Purported allosaurid-tyrannosaurid synapomorphies are seen to be largely size-related, present in the larger members of both clades, but absent in smaller members of the Tyrannosauridae. The remaining giant tetanurine theropods (Megalosaurus and Torvosaurus) were found to be progressively distant outgroups to an allosaurid-coelurosaur clade. The inclusion of the Tyrannosauridae within Maniraptora suggests a major adaptive radiation of coelurosaurs within Cretaceous Asiamerica comparable to contemporaneous radiations in various herbivorous dinosaurian clades.

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New anatomical information of the wukongopteridKunpengopterus sinensisWang et al., 2010 based on a new specimen

PeerJ ◽

10.7717/peerj.4102 ◽

2017 ◽

Vol 5 ◽

pp. e4102 ◽

Cited By ~ 3

Author(s):

Xin Cheng ◽

Shunxing Jiang ◽

Xiaolin Wang ◽

Alexander W.A. Kellner

Keyword(s):

Life Style ◽

Late Jurassic ◽

Dorsal Side ◽

Sesamoid Bones ◽

New Material ◽

Anatomical Information ◽

First Time

The Wukongopteridae compose a non-pterodactyloid clade of pterosaurs that are the most abundant flying reptiles in the deposits of the Middle-Late Jurassic Yanliao Biota. Until now, five species of three genera and two additional unnamed specimens have been described. Here we report on a new material, IVPP V 23674, that can be referred to the wukongopteridKunpengopterus sinensisdue to several features such as a comparably short nasoantorbital fenestra, the dorsally rising posterodorsal margin of the ischium, and the very short first pedal phalanx of digit V relative to metatarsal IV. IVPP V 23674 provides the first view of a wukongopterid palate, which differs from all other pterosaurs by having a very large postpalatine fenestra and laterally compressed choanae, indicating that the evolution of the pterosaur palate was more complex than previously thought. Sesamoid bones at the dorsal side of manual unguals are present and are reported for the first time in a wukongopterid suggesting an arboreal life-style for these pterosaurs.

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Remarkable teleostean fishes from the Late Jurassic of southern Germany and their phylogenetic relationships

Fossil Record ◽

10.5194/fr-3-137-2000 ◽

2000 ◽

Vol 3 (1) ◽

pp. 137-179 ◽

Cited By ~ 15

Author(s):

G. Arratia

Keyword(s):

New Taxa ◽

Phylogenetic Relationships ◽

Late Jurassic ◽

Sister Group ◽

Morphological Characters ◽

Phylogenetic Position ◽

New Genera ◽

Phylogenetic Hypothesis ◽

The Past ◽

New Information

Complete descriptions, as preservation permits, are provided for new Late Jurassic taxa (e.g., †Ascalabothrissops voelkli n. gen. and n. sp., †Anaethalion zapporum n. sp., and †Elopsomolos frickhingeri n. gen. and n. sp.); the phylogenetic positions of these taxa are given, as well as an evaluation of the European teleosts during the Late Jurassic. The relationships among certain fossil and extant teleosts are evaluated based on 191 unweighted morphological characters by using cladistic principles. The results suggest that †Ascalabothrissops n. gen. from the Kimmeridgian of Schamhaupten is the sister-taxon of †Pachythrissops from the Tithonian of Bavaria, and consequently is an ichthyodectiform. †Anaethalion zapporum n. sp., an elopiform, stands in an unresolved polytomy with †A. angustus, †A. knorri, and a clade formed by †A. angustissimus and more advanced elopiforms. The new results confirm Arratia (1997) that †Anaethalion, as presently understood, is a paraphyletic taxon. †Elopsomolos frickhingeri n. gen. and n. sp. forms a polytomy with †Elopsomolos sp. 1 and 3, and [Elops + Megalops]. Monophyly of the Kimmeridgian and Tithonian genus †Elopsomolos is not certain. Following the new phylogenetic hypothesis, that includes new taxa and new characters, the elopomorphs stand as the primitive sister-group of osteoglossomorphs and more advanced teleosts. The new information does not affect the phylogenetic position of the main extant teleostean clades and confirms previous results by Arratia (1991, 1996, 1997, 1999). The analysis of the elopiforms through time shows that the group had an important radiation during the Late Jurassic, to be replaced by new genera and species during the Cretaceous, and again during the Cenozoic. From numerous genera living in the past, elopiforms are represented now by two genera, Elops and Megalops. Soweit es die Erhaltung zulässt, werden vollständige Beschreibungen der drei neuen spätjurassischen Taxa †Ascalabothrissops voelkli n. gen. et n. sp., †Anaethalion zapporum n. sp., und †Elopsomolos frickhingeri n. gen. et n. sp. gegeben. Die phylogenetische Stellung dieser Taxa als auch anderer spätjurassischer europäischer Teleosteer ist analysiert. Die Verwandtschaftsbeziehungen innerhalb einiger fossiler und rezenter Teleosteer wurden auf der Basis von 191 nicht gewichteten morphologischen Merkmalen mit Hilfe der kladistischen Methode evaluiert. Als Ergebnis zeigt sich, dass †Ascalabothrissops n. gen. aus dem Kimmeridgium von Schamhaupten das Schwestertaxon von †Pachythrissops und damit ein Ichthyodectiformer ist. †Anaethalion zapporum n. sp., ein Elopiformer, steht in einer nicht auflösbaren Polytomie mit †A. angustus, †A, knorri, und einer Gruppe gebildet aus †A. angustissimus und weiter fortgeschrittenen Elopiformen. Die neuen Ergebnisse bestätigen Arratia (1997), dass †Anaethalion, wie zur Zeit umgrenzt, ein paraphylethisches Taxon darstellt. †Elopsomolos frickhingeri n. gen. et n. sp. bildet eine Polytomie mit †Elopsomolos sp. 1 und 3, und [Elops + Megalops]. Die Monophylie der Gattung †Elopsomolos aus dem Kimmeridgium und Tithonium ist nicht gesichert. Nach der neuen phylogenetischen Hypothese, die neue Taxa und neue Merkmale einbezieht, sind die Elopomorphen die primitive Schwestergruppe der Osteoglossomorphen und weiter fortgeschrittener Teleosteer. Die neuen Ergebnisse beeinflussen die phylogenetische Stellung der rezenten Hauptgruppen der Teleosteer nicht und bestätigen frühere Ergebnisse von Arratia (1991, 1996, 1997, 1999). Die Analyse der Elopiformen zeigt, dass die Gruppe eine bedeutende Radiation im Spätjura erlebte; neue Gattungen und Arten traten in der Kreide auf und dann wieder im Känozoikum. Im Gegensatz zu den zahlreichen fossilen Gattungen sind die Elopiformen heute nur durch zwei Gattungen vertreten, Elops und Megalops. doi:<a href="http://dx.doi.org/10.1002/mmng.20000030108" target="_blank">10.1002/mmng.20000030108</a>

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Isolated pliosaurid teeth from the Albian–Cenomanian (Cretaceous) of Annopol, Poland

Acta Geologica Polonica ◽

10.1515/agp-2017-0018 ◽

2017 ◽

Vol 67 (3) ◽

pp. 393-403 ◽

Cited By ~ 8

Author(s):

Daniel Madzia ◽

Marcin Machalski

Keyword(s):

Cross Section ◽

Late Cretaceous ◽

Type Species ◽

Late Jurassic ◽

Morphological Variability ◽

Original Material ◽

Tooth Crown ◽

Similar Morphology ◽

Faunal Turnover ◽

Early Late

AbstractBrachauchenine pliosaurids were a cosmopolitan clade of macropredatory plesiosaurs that are considered to represent the only pliosaurid lineage that survived the faunal turnover of marine amniotes during the Jurassic- Cretaceous transition. However, the European record of the Early to early Late Cretaceous brachauchenines is largely limited to isolated tooth crowns, most of which have been attributed to the classic Cretaceous taxon Polyptychodon. Nevertheless, the original material of P. interruptus, the type species of Polyptychodon, was recently reappraised and found undiagnostic. Here, we describe a collection of twelve pliosaurid teeth from the upper Albian-middle Cenomanian interval of the condensed, phosphorite-bearing Cretaceous succession at Annopol, Poland. Eleven of the studied tooth crowns, from the Albian and Cenomanian strata, fall within the range of the morphological variability observed in the original material of P. interruptus from the Cretaceous of England. One tooth crown from the middle Cenomanian is characterized by a gently subtrihedral cross-section. Similar morphology has so far been described only for pliosaurid teeth from the Late Jurassic and Early Cretaceous. Even though it remains impossible to precisely settle the taxonomic distinctions, the studied material is considered to be taxonomically heterogeneous.

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The postcranial skeleton, phylogenetic position, and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps

Canadian Journal of Earth Sciences ◽

10.1139/e02-082 ◽

2003 ◽

Vol 40 (4) ◽

pp. 527-556 ◽

Cited By ~ 44

Author(s):

Michael deBraga

Keyword(s):

South Africa ◽

Morphological Study ◽

Lower Triassic ◽

Sister Group ◽

Phylogenetic Position ◽

Sister Group Relationship ◽

Early Triassic ◽

Postcranial Skeleton ◽

Sister Clade ◽

Key Innovations

A morphological study of the postcranial skeleton of Procolophon trigoniceps from the Lower Triassic of South Africa and Antarctica is undertaken. Procolophon shares a sister-group relationship with the procolophonid Tichvinskia from the Lower Triassic of Russia and is a basal member of Procolophonidae. This clade also includes the enigmatic taxon Sclerosaurus, believed most recently to be a pareiasaur relative. Owenettids form a separate lineage from Procolophonidae and are predominantly restricted to the Permian of both South Africa and Madagascar. A phylogenetically based assessment is considered, in which specialized modern taxa (sand lizards) are compared to their nonfossorial sister clade, allowing for "key innovations" to be identified. A similar comparison between owenettids and procolophonids reveals a number of apparent "key innovations" within procolophonids that are suggestive of a burrowing lifestyle for Procolophon.

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