REAPPRAISAL OF THE MORPHOLOGY AND PHYLOGENETIC RELATIONSHIPS OF THE ALLIGATOROID CROCODILIAN DIPLOCYNODON HANTONIENSIS (OWEN, 1846) FROM THE EOCENE OF HORDWELL, UNITED KINGDOM (original) (raw)
Related papers
Zoological Journal of the Linnean Society, 2014
Crocodilian remains from the late Palaeocene continental locality of Mont de Berru (Marne, France) offer the opportunity to reassess the taxonomic identity of the oldest diplocynodontid from Europe. Owing to significant morphological differences from previously described species of Diplocynodon, which include the presence of a splenial symphysis, a new species, Diplocynodon remensis sp. nov., is erected here. Its inclusion in a phylogenetic framework for Eusuchia leads to its positioning as a derived member of diplocynodontids. Diplocynodontidae are viewed as a basal alligatoroid taxon, and, because morphological affinities with the Late Cretaceous−early Eocene North American genus Borealosuchus were mentioned in earlier studies, a comparison amongst D. remensis sp. nov., Leidyosuchus, and Borealosuchus spp. is presented. Although D. remensis sp. nov. is the geologically oldest diplocynodontid, according to our results, it is not the phylogenetically most primitive. Other morphological discrepancies are highlighted, indicating that the topology recovered here is only tentative. From a biogeographical point of view, the appearance of Diplocynodon in Europe prior to the Palaeocene/Eocene boundary indicates that it did not disperse with North American taxa that reached Europe around the time of the Palaeocene-Eocene thermal maximum (PETM). Therefore, a pre-PETM dispersal from North America at the same times as other vertebrates with clear North American affinities also occurring in the Palaeocene of Europe cannot be excluded. The description of D. remensis sp. nov. adds substantial new, albeit conflicting, information, highlighting the need for a better phylogenetic framework with a revision of other critical taxa (Menatalligator, Borealosuchus) from the Palaeocene of Europe and North America.
Vorume 2 M-Z Entrno av Rotnlo Slncrn 1338 ENCYCLOPEDIA OF PALEONTOLOGY 1919. The structure, evolution and origin of the Amphibia: The "orders" Rachitomi and Stereospon dyli' Philosophical Tiansactions ofthe Ro4al Societ7 ofLondon' ser' B' 209:1-73. Ig26.Theevolution and origin of the Amphibia' Philosophica/ Tlansactions ofthe Royal Society ofLondon' ser' B' 214:189-257. 795I . Paleontohgq antl Modern Biology' New Haven' Connecticut: Yale University Press. WESTOLL, THOMAS STANLEY English, Lg1-2-95 \Testoll made original contributions to our knowledge of the structure and relati-onships of early vertebrates, especially by clarifi,ing concepts of dermal bone homologies (similarity of structures due to common ancestry) in the sarcopterygians (crossopterygians' dipnoans) and tetrapods. Many of lWestoll's works are character-
Paleobiologists must propose a priori hypotheses of homology when conducting a phylogenetic analysis of extinct taxa. The distributions of such “primary” homologies among species are fundamental to phylogeny reconstruction because they reflect a prior belief in what constitutes comparable organismal elements and are the principal determinants of the outcome of phylogenetic analysis. Problems arise when fossil morphology presents seemingly equivocal hypotheses of homology, herein referred to as antinomies. In groups where homology recognition has been elusive, such as echinoderms, these problems are commonly accompanied by the presence (and persistence) of poor descriptive terminology in taxonomic literature that confounds an understanding of characters and stymy phylogenetic research. This paper combines fossil morphology, phylogenetic systematics, and insights from evolutionary developmental biology to outline a research program in Phylogenetic Paleo-ontogeny. A “paleo” ontogenetic approach to character analysis provides a logical basis for homology recognition and discerning patterns of character evolution in a phylogenetic context. To illustrate the utility of the paleo-ontogenetic approach, I present a reassessment of historically contentious plate homologies for “pan-cladid” crinoids (Cladida, Flexibilia, Articulata). Developmental patterns in living crinoids were combined with the fossil record of pan-cladid morphologies to investigate primary posterior plate homologies. Results suggest the sequence of morphologic transitions unfolding during the ontogeny of extant crinoids are developmental relics of their Paleozoic precursors. Developmental genetic modules controlling posterior plate development in pan-cladid crinoids have likely experienced considerable constraint for over 250 million years and limited morphologic diversity in the complexity of calyx characters. Future phylogenetic analyses of pan-cladids are recommended to consider the presence of a single plate in the posterior region homologous with the radianal, rather than the anal X, as is commonly assumed.
Comptes Rendus Palevol, 2017
We describe crocodylian remains from the Early Miocene (MN4) site of Els Casots (Subirats, Vallès-Penedès Basin, NE of the Iberian Peninsula). Referral to Diplocynodon (Alligatoroidea: Diplocynodontidae) is justified by several cranial and postcranial features, including: (1) the subequal and confluent alveoli of the maxilla (fourth and fifth) and dentary (third and fourth); (2) the position of the foramen aëreum on the quadrate; (3) the small and ventrally reflected medial hemicondyle of the quadrate; (4) the distinct dorsoventral step on the frontal; and (5) the bipartite ventral osteoderms. Multiple morphological features are consistent with an attribution to Diplocynodon ratelii, previously known from the Early Miocene (MN2) of France, and discount an alternative attribution to other species of the genus, including Diplocynodon ungeri from the Middle Miocene (MN5) of Austria. The described material from Els Casots is smaller in size than the French material of D. ratelii, possibly reflecting an earlier ontogenetic stage. The described remains constitute the first report of D. ratelii and the youngest record of Diplocynodon in the Iberian Peninsula, where only Diplocynodon muelleri and Diplocynodon tormis have been previously reported. The presence of Diplocynodon further supports the lacustrine depositional environment previously inferred for Els Casots and also indicates a relatively high temperature.
Large-scale molecular datasets have generally outperformed morphological data for inferring phylogeny, and sources of error in the latter are poorly understood. The morphologically and ecologically diverse marsupial order Diprotodontia (kangaroos and their relatives, the koala, wombats and possums) is well suited to considering these issues. Recent molecular results provide a phylogenetic benchmark for comparing previous molecular and morphological studies, encompassing all of the major phylogenetic data sources and methods that have been employed over the past 50 years. We show here that most molecular methodologies and 'informal-comparative' morphological studies have inferred diprotodontian relationships that closely resemble the recent molecular consensus. However, and perhaps surprisingly, algorithmic morphology, such as maximum parsimony analysis of morphological matrices, has inferred markedly inaccurate phylogenies, and is not improved by re-analysis with more recently developed, model-based (e.g., likelihood and Bayesian) methods. This is particularly concerning because algorithmic morphology is the primary approach for integrating fossils into the tree of life, and hence, for both calibrating molecular timescales and extending phylogenetic inferences of evolutionary processes beyond the snapshot provided by modern species. A novel simulation study presented here suggests that the inaccuracies in the marsupial algorithmic morphology studies partly stem from functional and body-size correlations among taxa that override phylogenetic signals. We use the results to trial a reverse engineered phylogeny approach to correcting for such functional and developmental correlations among morphological data. In addition, we interrogated a newly published, densely taxonsampled morphological matrix. Deeper level phylogeny reconstruction was improved by including fossils alongside extant taxa and counterintuitively, by increased effort to resolve relationships among shallow taxa.
Alcheringa, 2011
A comprehensive understanding of morphological and morphometrical variation for systematically important characters is a prerequisite for reliable taxonomic analyses of extinct morphospecies. However, perception of such variation is commonly limited due to a paucity of fossil material that forms the basis of such analyses. Here we report a new record of Pleistocene Diprotodon optatum Owen, 1838 (Diprotodontoidea) represented by near-complete upper tooth rows that exhibit a high degree of individual variation within systematically important upper premolars. The individual possesses features (e.g. development of parastyle, anterocristae and anterior longitudinal groove) that are considered to be close to the polar extremes of premolar variation within the morphospecies, but occurring on either side of the palate. Although such morphologies were previously recognized on the basis of isolated specimens, they have never been observed as having occurred on either side of the tooth row within a single indvidual. The observation of such extreme variation in premolar form within a single individual means that although the diprotodontoid P3 may serve some systematic importance in distinguishing certain taxa, the weight placed upon perceived differences within any single character of the premolar must be gauged by an understanding of broader variation within the group.
Crocodiles are a conservative group of reptiles regarding their morphology and behaviour. Available Fossils are hence important to be studied for phylogeny, taxonomy and morphology. A fossil fragmentary crocodilian skull was found in lignite clay in the Paleogene sedimentary area from the Middle Oligocene Epoch of Sieglitz near Camburg at Saale river in Central Germany. This 20th century discovery documents a new species of Diplocynodon (Diplocynodon Haeckeli, described by Seidlitz in 1917). Another crocodile fossil was unearthed in 1878 from the Eocene Epoch, of Haunsberg near Sankt Pankraz in the province of Salzburg in Austria, which had been missing since 1970 and was recently rediscovered and identified. This rediscovered specimen, representing a crocodile mandible and an isolated tooth, which could belong to Asiatosuchus and not Diplocynodon. However, the morphology of isolated tooth is not a reliable source to identify it up to the generic level, so open taxonomy is used here for identification, it may be associated to the same or a new species. The new discoveries of fossils provide new characters enhancing our knowledge on a particular taxon and on the whole group.