Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recogni... more Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptive scenarios for primate origins for nearly a half-century. Likewise, palaechthonids have been considered important for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62 Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first postcranial elements recovered for a palaechthonid. Results from a cladistic analysis that includes new data from this skeleton suggest that palaechthonids are a paraphyletic group of stem primates, and that T. wilsoni is most closely related to paromomyids. New evidence from the appendicular skeleton of T. wilsoni fails to support an influential hypothesis based on inferences from craniodental morphology that palaechthonids were terrestrial. Instead, the postcranium of T. wilsoni indicates that it was similar to that of all other plesiadapiforms for which skeletons have been recovered in having distinct specializations consistent with arboreality
Sixty-five million years ago, as the last of the non-avian dinosaurs were going extinct, our earl... more Sixty-five million years ago, as the last of the non-avian dinosaurs were going extinct, our earliest recognized ancestors appeared in the fossil record. When, where, and why did they evolve?
American journal of physical anthropology, Jan 18, 2015
Extant euprimates (=crown primates) have a characteristically expanded neocortical region of the ... more Extant euprimates (=crown primates) have a characteristically expanded neocortical region of the brain relative to that of other mammals, but the timing of that expansion in their evolutionary history is poorly resolved. Examination of anatomical landmarks on fossil endocasts of Eocene euprimates suggests that significant neocortical expansion relative to contemporaneous mammals was already underway. Here, we provide quantitative estimates of neocorticalization in stem primates (plesiadapiforms) relevant to the question of whether relative neocortical expansion was uniquely characteristic of the crown primate radiation. Ratios of neocortex to endocast surface areas were calculated for plesiadapiforms using measurements from virtual endocasts of the paromomyid Ignacius graybullianus (early Eocene, Wyoming) and the microsyopid Microsyops annectens (middle Eocene, Wyoming). These data are similar to a published estimate for the plesiadapid, Plesiadapis tricuspidens, but contrast with t...
To discover interordinal relationships of living and fossil placental mammals and the time of ori... more To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats). Our tree suggests that Placentalia first split into Xenarthra and Epitheria; extinct New World species are the oldest members of Afrotheria.
Proceedings of the National Academy of Sciences of the United States of America, Jan 23, 2007
Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchon... more Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchontan mammals (tree shrews and flying lemurs). We report results from a comprehensive cladistic analysis using cranial, postcranial, and dental evidence including data from recently discovered Paleocene plesiadapiform skeletons (Ignacius clarkforkensis sp. nov.; Dryomomys szalayi, gen. et sp. nov.), and the most plesiomorphic extant tree shrew, Ptilocercus lowii. Our results, based on the fossil record, unambiguously place plesiadapiforms with Euprimates and indicate that the divergence of Primates (sensu lato) from other euarchontans likely occurred before or just after the Cretaceous/Tertiary boundary (65 Mya), notably later than logistical model and molecular estimates. Anatomical features associated with specialized pedal grasping (including a nail on the hallux) and a petrosal bulla likely evolved in the common ancestor of Plesiadapoidea and Euprimates (Euprimateformes) by 62 Mya in e...
Page 155. Chapter 5 Unusual Vertebrate Microfaunas From the Willwood Formation, Early Eocene of t... more Page 155. Chapter 5 Unusual Vertebrate Microfaunas From the Willwood Formation, Early Eocene of the Bighorn Basin, Wyoming MARY T. SILCOX and KENNETH D. ROSE 1. Introduction 131 2. Materials and Methods 133 2.1. ...
Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recogni... more Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptive scenarios for primate origins for nearly a half-century. Likewise, palaechthonids have been considered important for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62 Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first postcranial elements recovered for a palaechthonid. Results from a cladistic analysis that includes new data from this skeleton suggest that palaechthonids are a paraphyletic group of stem primates, and that T. wilsoni is most closely related to paromomyids. New evidence from the appendicular skeleton of T. wilsoni fails to support an influential hypothesis based on inferences from craniodental morphology that palaechthonids were terrestrial. Instead, the postcranium of T. wilsoni indicates that it was similar to that of all other plesiadapiforms for which skeletons have been recovered in having distinct specializations consistent with arboreality
Sixty-five million years ago, as the last of the non-avian dinosaurs were going extinct, our earl... more Sixty-five million years ago, as the last of the non-avian dinosaurs were going extinct, our earliest recognized ancestors appeared in the fossil record. When, where, and why did they evolve?
American journal of physical anthropology, Jan 18, 2015
Extant euprimates (=crown primates) have a characteristically expanded neocortical region of the ... more Extant euprimates (=crown primates) have a characteristically expanded neocortical region of the brain relative to that of other mammals, but the timing of that expansion in their evolutionary history is poorly resolved. Examination of anatomical landmarks on fossil endocasts of Eocene euprimates suggests that significant neocortical expansion relative to contemporaneous mammals was already underway. Here, we provide quantitative estimates of neocorticalization in stem primates (plesiadapiforms) relevant to the question of whether relative neocortical expansion was uniquely characteristic of the crown primate radiation. Ratios of neocortex to endocast surface areas were calculated for plesiadapiforms using measurements from virtual endocasts of the paromomyid Ignacius graybullianus (early Eocene, Wyoming) and the microsyopid Microsyops annectens (middle Eocene, Wyoming). These data are similar to a published estimate for the plesiadapid, Plesiadapis tricuspidens, but contrast with t...
To discover interordinal relationships of living and fossil placental mammals and the time of ori... more To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats). Our tree suggests that Placentalia first split into Xenarthra and Epitheria; extinct New World species are the oldest members of Afrotheria.
Proceedings of the National Academy of Sciences of the United States of America, Jan 23, 2007
Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchon... more Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchontan mammals (tree shrews and flying lemurs). We report results from a comprehensive cladistic analysis using cranial, postcranial, and dental evidence including data from recently discovered Paleocene plesiadapiform skeletons (Ignacius clarkforkensis sp. nov.; Dryomomys szalayi, gen. et sp. nov.), and the most plesiomorphic extant tree shrew, Ptilocercus lowii. Our results, based on the fossil record, unambiguously place plesiadapiforms with Euprimates and indicate that the divergence of Primates (sensu lato) from other euarchontans likely occurred before or just after the Cretaceous/Tertiary boundary (65 Mya), notably later than logistical model and molecular estimates. Anatomical features associated with specialized pedal grasping (including a nail on the hallux) and a petrosal bulla likely evolved in the common ancestor of Plesiadapoidea and Euprimates (Euprimateformes) by 62 Mya in e...
Page 155. Chapter 5 Unusual Vertebrate Microfaunas From the Willwood Formation, Early Eocene of t... more Page 155. Chapter 5 Unusual Vertebrate Microfaunas From the Willwood Formation, Early Eocene of the Bighorn Basin, Wyoming MARY T. SILCOX and KENNETH D. ROSE 1. Introduction 131 2. Materials and Methods 133 2.1. ...
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Papers by Mary T Silcox
for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62 Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first postcranial elements recovered for a palaechthonid. Results from a cladistic analysis that includes new data from this skeleton suggest that palaechthonids are a paraphyletic group of stem primates, and that T. wilsoni is most closely related to paromomyids. New evidence from the appendicular skeleton of T. wilsoni fails to support an influential hypothesis based on inferences from craniodental morphology that palaechthonids were terrestrial. Instead, the postcranium of T. wilsoni indicates that it was similar to that of all other plesiadapiforms for which skeletons have been recovered in having distinct specializations consistent with arboreality
for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62 Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first postcranial elements recovered for a palaechthonid. Results from a cladistic analysis that includes new data from this skeleton suggest that palaechthonids are a paraphyletic group of stem primates, and that T. wilsoni is most closely related to paromomyids. New evidence from the appendicular skeleton of T. wilsoni fails to support an influential hypothesis based on inferences from craniodental morphology that palaechthonids were terrestrial. Instead, the postcranium of T. wilsoni indicates that it was similar to that of all other plesiadapiforms for which skeletons have been recovered in having distinct specializations consistent with arboreality