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Phylogeny of the Taeniodonta: Evidence from Dental Characters and Stratigraphy

Taylor & Francis
Journal of Verterbrate Paleontology
Authors:
Deborah L. Rook
Deborah L. Rook
John Paul Hunter at The Ohio State University
John Paul Hunter
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The Taeniodonta is a group of eutherian mammals from the Paleogene of North America, which evolved rapidly in the Paleocene to achieve, in some forms, large body size, hypselodont (i.e., evergrowing) canine and postcanine teeth, and peculiar patterns of tooth wear. Eleven genera of taeniodonts occur in two subgroups, recognized at the level of families or subfamilies depending on author, the Conoryctidae and the Stylinodontidae. There has not been a comprehensive computer-assisted phylogenetic analysis of the taeniodonts, and questions have arisen over the monophyly of the taeniodonts and the conoryctids. Cladistic analyses based on thirty-seven dental characters using NONA and Winclada showed that two subclades of Taeniodonta are well supported, a clade consisting of the conoryctids exclusive of Onychodectes (i.e., Conoryctella, Conoryctes, and Huerfanodon) and a clade consisting of all the known stylinodontids (Wortmania, Schochia, Psittacotherium, Ectoganus, and Stylinodon). Stratocladistic analysis, which takes into account the temporal sequence of taxa in the fossil record, supports the results of the morphological analysis. The Late Cretaceous taeniodont Schowalteria occupies the most basal position in taeniodont phylogeny, pre-dating an inferred conoryctid–stylinodontid split in the early Paleocene, and establishing the taeniodonts as monophyletic.
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... Character 34: We find that the M2 of Wortmania (based on NMMNH P-9000 and P-64001) is “subequal in size with, or slightly smaller than, M1” (2) rather than “shorter but more transverse than M1” (1), following Rook and Hunter’s [8] scoring for “Schochia” for this character (see Table 1). ...
... Following from the above discussion, we ran a revised version of the Rook and Hunter [8] matrix. “Robertschochia” (“Schochia”) was removed from the analysis because we consider this taxon to be a subjective junior synonym of Wortmania (see above). ...
... The results of our analyses differ from the phylogeny obtained by Rook and Hunter ( [8]: Figure 1) in several respects. First, Onychodectes is placed in a more basal position, basal to all conoryctid and stylinodontid taeniodonts whereas Rook and Hunter [8] found Onychodectes as the sister taxon to Stylinodontidae (i.e., nested between Conoryctidae and Stylinodontidae on the phylogeny). ...
New Specimens of the Rare Taeniodont Wortmania (Mammalia: Eutheria) from the San Juan Basin of New Mexico and Comments on the Phylogeny and Functional Morphology of "Archaic" Mammals
Article
Full-text available
Background: Taeniodonta is a clade of Late Cretaceous-Paleogene mammals remarkable for their relatively extreme cranial, dental, and postcranial adaptations and notable for being among the first mammals to achieve relatively large size following the Cretaceous-Paleogene mass extinction. Previous workers have hypothesized that taeniodonts can be divided into two clades: Conoryctidae, a group of small-bodied taeniodonts with supposedly "generalized" postcranial skeletons, and Stylinodontidae, a group of large-bodied, robust animals with massive forelimbs and claws adapted for scratch-digging. However, many taeniodont taxa are poorly known and few are represented by postcranial material, leaving many details about their anatomy, biology, and evolution ambiguous. Methodology/principal findings: In this paper, we describe three new specimens of the rare taxon Wortmania otariidens from the early Paleocene (Puercan) of New Mexico. Among these specimens is one that includes remarkably complete cranial and dental material, including associated upper and lower teeth, and another that consists of partial forelimbs. These specimens allow for an updated anatomical description of this unusual taxon, supply new data for phylogenetic analyses, and enable a more constrained discussion of taeniodont biology and functional morphology. Conclusions/significance: The new specimen of Wortmania that includes associated upper and lower teeth indicates that previous interpretations of the upper dentition of this taxon were not accurate and the taxon Robertschochia sullivani is a junior synonym of W. otariidens. New specimens that include partial forelimbs indicate that Wortmania is very similar to later, large-bodied taeniodonts, with marked and distinctive adaptations for scratch-digging. Comparisons with other taeniodont taxa that include postcranial material suggest that all taeniodonts may have had scratch-digging adaptations. A phylogenetic analysis shows that Schowalteria and Onychodectes are basal taeniodonts, Stylinodontidae (including Wortmania) is monophyletic, and a monophyletic Conoryctidae (but not including Onychodectes) is only recovered when certain characters are ordered.
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... We also test the hypothesis that taeniodonts are members of the crown group of Eutheria. In order to accomplish these goals, we adapted character sets already used to explore the relationships among taeniodonts and their presumed close relatives (Schoch 1986; Eberle 1999; Rook et al. 2010; Rook and Hunter 2011) and the best dataset available at the present time for testing crown or stem group status of extinct eutherians (Wible et al. 2007Wible et al. , 2009). ...
... For investigation into the stem or crown group membership of the Taeniodonta, we used the published character matrix of Wible et al. (2009). Schowalteria, the most basal taeniodont (according to Rook et al. 2010; Rook and Hunter 2011) and Alveugena, the purported sister taxon (Eberle 1999; Rook et al. 2010) were added (see Appendix 2 for character definitions and codes of added taxa). ...
... Schowalteria is the sister group to the rest of the taeniodonts (as also in Rook and Hunter 2011), no longer contradicting its early appearance in the fossil record. There are also no autapomorphic characters in this analysis precluding Schowalteria from being the ancestral taeniodont (Rook and Hunter 2011). Accordingly, we rediagnose the monophyletic Taeniodonta in the final section of this paper to include Schowalteria and all other taeniodonts. ...
Rooting Around the Eutherian Family Tree: The Origin and Relations of the Taeniodonta
Article
Full-text available
  • Mar 2013
  • J Mamm Evol
Placing early groups into the overall phylogeny of eutherian mammals can be challenging, particularly when the group does not have extant members. We investigated the relationships of the Taeniodonta, an extinct group from the Late Cretaceous through Paleogene of North America. This group has a few purported close relatives, including Cimolestes, Procerberus, and Alveugena, that may form a sequence of ancestors and descendants. The leading hypothesis is that Procerberus gave rise to taeniodonts through Alveugena. We test this hypothesis and analyze relations to known stem and crown Eutheria to determine the place of taeniodonts in eutherian phylogeny. Cladistic analyses were performed using previously published characters and datasets, namely a taeniodont/cimolestid specific dataset and a reanalysis of Wible and colleagues (2009), with added taxa for both. Our studies suggest that taeniodonts arose from Cimolestes through Alveugena, that Procerberus is more distantly related to taeniodonts, and that taeniodonts and their relatives are stem eutherians. We diagnose the Taeniodonta based on these analyses. Other Paleogene groups, especially those allied with Cimolestes such as tillodonts and pantolestans, merit further study. Our findings indicate that stem eutherians such as the Taeniodonta, in addition to crown eutherians, continued to diversify during the Paleogene.
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... Williamson and Brussette (2013) described new material of the taeniodont Wortmania and commented on previous interpretations of the phylogeny of the taeniodonts. They revised the character matrix used by Rook and Hunter (2011) and tested the consequences of treating multistate characters as ordered or unordered in their phylogenetic analyses. Differing from Rook and Hunter (2013) they interpret the species of Procerberus as more closely related to Alveugena and the Taeniodonta than to Cimolestes. ...
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... Stratocladistics incorporates stratigraphic data into cladistic analyses (see, for example, refs. [43][44][45][46][47][48]. A stratocladistic analysis was performed using the program StrataPhy, which produces trees that can indicate possible ancestordescendant relationships (49). ...
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Assessing the Adequacy of Morphological Models used in Palaeobiology
Preprint
Full-text available
  • Jan 2024
Reconstructing the evolutionary history of different groups of organisms provides insight into how life originated and diversified on Earth. Phylogenetic trees are commonly used to estimate this evolutionary history, providing a hypothesis of the events. Within Bayesian phylogenetics a major step in estimating a tree is in choosing an appropriate model of character evolution. In the case of most extinct species, our only source of information to decipher their phylogenetic relationships is through the morphology of fossils. We therefore use a model of morphological character evolution, the most common of which being the Mk Lewis model. While it is frequently used in palaeobiology, it is not known whether the simple Mk substitution model, or any extensions to it, provide a sufficiently good description of the process of morphological evolution. To determine whether or not the Mk model is appropriate for fossil data we used posterior predictive simulations, a model adequacy approach, to estimate absolute fit of the model to morphological data sets. We first investigate the impact that different versions of the Mk model have on key parameter estimates using tetrapod data sets. We show that choice of substitution model has an impact on both topology and branch lengths, highlighting the importance of model choice. Next, we use simulations to investigate the power of posterior predictive simulations for morphology. Having validated this approach we show that current variations of the Mk model are in fact performing adequately in capturing the evolutionary dynamics that generated our data. We do not find any preference for a particular model extension across multiple data sets, indicating that there is no ‘one size fits all’ when it comes to morphological data and that careful consideration should be given to choosing models of discrete character evolution. By using suitable models of character evolution, we can increase our confidence in our phylogenetic estimates, which should in turn allow us to gain more accurate insights into the evolutionary history of both extinct and extant taxa.
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The status of Schowalteria clemensi , the Late Cretaceous taeniodont (Mammalia)
Article
  • Sep 2016
Schowalteria clemensi Fox and Naylor, from the latest Cretaceous lower Scollard Formation, Red Deer Valley, Alberta, is the only known Mesozoic member of the extinct mammalian order Taeniodonta. Schowalteria clemensi was originally classified in the derived family Stylinodontidae, but more recent studies employing computer-assisted phylogenetic and stratocladistic analyses of taeniodont interrelationships contend that S. clemensi is the basal taeniodont, whereas Onychodectes, long considered the basal taeniodont, is instead the sister group of stylinodontids alone. These studies, however, are deeply flawed, marred by selection of problematic outgroups, incorrect scoring of numerous character states and of the stratigraphic age of S. clemensi, omission of all stylinodontid-like characters of S. clemensi, and reliance on major, implausible reversals during early taeniodont history. The more recent of these analyses also examined the relationship of taeniodonts within Eutheria, but this data set includes 54 (61%) erroneous scores for S. clemensi, the only taeniodont in the analysis. Moreover, subsequently published errata introduced new errors into the analyses. Thus, the hypothesis that S. clemensi is the earliest discovered stylinodontid remains unrefuted by these studies: the earliest history of stylinodontids and that of more basal taeniodonts is still to be discovered, among species older than S. clemensi itself. Citation for this article: Fox, R. C. 2016. The status of Schowalteria clemensi, the Late Cretaceous taeniodont (Mammalia). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1211666.
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A revision of the Late Cretaceous–Paleocene eutherian mammal Cimolestes Marsh, 1889
Article
  • Nov 2015
  • CAN J EARTH SCI
Cimolestes Marsh is a North American eutherian mammal primarily known from latest Cretaceous deposits in Alberta, Wyoming, Saskatchewan, and Montana. At present, five species of Cimolestes are considered valid, all Lancian in age; they include one of the largest North American Late Cretaceous therian mammals as well as one of the smallest, a size range far exceeding that within other genera of tribosphenic therians contemporary with Cimolestes, such as the leptictoid eutherian Gypsonictops Simpson or genera of alphadontid or pediomyid marsupials. Moreover, the species of Cimolestes display a disparity of dental morphology in addition to size well in excess of interspecific differences within these genera. Given these considerations, Cimolestes is clearly a grade-taxon, uniting species sharing an adaptively subzalambdodont dentition, but showing divergent specializations within this pattern that are inconsistent with monophyly of its presently included species. To correct these imbalances, this paper limits Cimolestes to Cimolestes incisus Marsh and Cimolestes stirtoni Clemens; Cimolestes magnus Clemens and Russell, Cimolestes cerberoides Lillegraven, and Cimolestes propalaeoryctes Lillegraven are reclassified in the new genera Altacreodus, Ambilestes, and Scollardius, respectively. Altacreodus magnus, having a massive shearing dentition, is reconfirmed as showing a relationship to some Tertiary ‘creodonts’ not shared by other species of Lancian cimolestids; Ambilestes cerberoides exhibits a distinctive molar wear pattern that emphasized horizontal grinding, not orthal shear; Scollardius propalaeoryctes, the smallest species in this revision and having hyper-faunivorous molars, was not ancestral to Paleogene Palaeoryctidae, as indicated in part by contradictions in premolar number and morphology. © 2015, Canadian Journal of Earth Science. All rights reserved.
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Trait-based diversification shifts reflect differential extinction among fossil taxa
Article
Full-text available
  • Oct 2014
Significance Shifts in biological diversity often are associated with particular anatomical traits. Anatomical data from over 300 clades of brachiopods, molluscs, arthropods, echinoderms, and chordates show that trait-based diversification shifts are common at even fairly low (genus and species) taxonomic levels. Cambrian taxa present the lone major exception. Among post-Cambrian taxa, diversification shifts correlate strongly with elevated net extinction of primitive taxa rather than elevated net speciation of derived taxa or increased morphological disparity among derived taxa. This finding emphasizes the importance of extinction in shaping morphological and phylogenetic diversity among closely related species and genera as well as suggests another way in which Cambrian evolution was unique.
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Cf.Wortmaniafrom the early Paleocene of Montana and an evaluation of the fossil record of the initial diversification of the Taeniodonta (Mammalia)1,2
Article
  • Mar 2013
  • CAN J EARTH SCI
The Garbani Channel deposits, part of the Tullock Formation exposed in northeastern Montana, have yielded a large sample of vertebrates that probably lived during the Puercan 3 North American Land Mammal Age (NALMA). Four fossils in this sample — three isolated teeth and a medial phalanx — document the presence of a stylinodontid taeniodont, cf. Wortmania. Discovery of cf. Wortmania in the Tullock Formation extends the documented range of taeniodonts during Puercan 3 approximately 500 miles (800 km) northward from the San Juan Basin, New Mexico. Evaluation of the oldest records of taeniodonts, from the Lancian, Puercan, and Torrejonian NALMAs, highlights biases warranting future research. Recent phylogenetic analyses that resulted in numerous ghost lineages indicate that the available fossil record is far from complete. They open the possibility that the origin and initial radiation of taeniodonts occurred in areas yet to be sampled and their first occurrences might reflect immigration of invasive species. The available fossil record of taeniodonts is biased with significantly more abundant and complete specimens discovered in the San Juan Basin than at localities to the north. This bias is also apparent in the available samples of two other lineages of large Puercan mammals, the multituberculate Taeniolabis and the “triisodontid” Eoconodon. Where they occur, taeniodonts are relatively rare members of any local fauna. Is their rarity a product of an ecological bias or a reflection of decreasing population size related to increasing body size?
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Phylogenetic Analysis: The Basic Method
Chapter
Full-text available
  • Jan 2002
Systematics has a unique place among natural sciences because it is the most evolutionary of all sciences. It is strictly historical rather than experimental. Of course, many of the restrictions on systematics are found elsewhere. For example, neither systematists nor astronomers can perform manipulative experiments to see if what they observe will happen again in the evolution of life or stars. Sciences that focus on history have special problems and appropriate epistemologies (rules about how we establish the validity of what we know, see [1]). Systematics is unique in requiring that every practicing authority know all the work that ever came before,both good and bad. In physics
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Bridging the transition between Didelphodonts and Taeniodonts
Article
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StrataPhy: A new computer program for stratocladistic analysis
Article
  • Jan 2008
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A Late Cretaceous taeniodont (Eutheria, Mammalia) from Alberta, Canada
Article
  • Sep 2003
  • Neues Jahrbuch Geol Palaontol Abhand
Schowalteria clemensi n.g. n.sp., from the Late Cretaceous Scollard Formation, Red Deer River Valley is the first Mesozoic taeniodont to be discovered. Although more primitive in important features of the postcanine dentition than the conoryctid Onychodectes (of mid-Puercan age, New Mexico, and previously the most primitive tacniodont known), S. clemensi most resembles the advanced, stylinodontid taeniodonts in incisor morphology, canine specializations, facial proportions, and zygomatic arch construction. The dentition of Schowalteria indicates that the purported affinity of palaeoryctid insectivorans with Onychodectes is based only on homoplastic resemblances, leaving taeniodont relationships unresolved.
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New Conoryctines (Mammalia: Taeniodonta) from the Middle Paleocene (Torrejonian) of Western North America
Article
  • Nov 1981
A new genus and species of conoryctine taeniodont is described from two skulls and associated lower jaw fragments from middle Paleocene-aged (Torrejonian) strata of the Nacimiento Formation, San Juan Basin, New Mexico. A second new species, known from a lower jaw from Torrejonian-aged strata of the Polecat Bench Formation, Big Horn Basin, Wyoming, also is described. Among the conoryctines, the new genus most closely resembles Conoryctes, but differs from it in having a relatively molarized P3, prominent mesostyles on M1–2, and relatively prominent paraconids and paracristids on the lower molars. “Triisodon heilprinianus” Cope 1882, recently referred to Conoryctes comma, tentatively is referred to the new genus and is considered a nomen dubium at the specific level.
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A New Taeniodont from the Paleocene of the San Juan Basin, New Mexico
Conference Paper
  • Jan 1990
We describe a new genus and species of taeniodont from the early Paleocene (Puercan) of the San Juan Basin, New Mexico. This new taeniodont combines derived features of the upper premolars with primitive upper molars and thus forces a reassessment of taeniodont phylogeny that recognizes Conoryctidae as a paraphyletic taxon.
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