TY - JOUR
T1 - Evolution of early Eocene Palaeosinopa (Mammalia, Pantolestidae) in the Willwood Formation of the Bighorn Basin, Wyoming
AU - Dunn, Rachel H.
AU - Rose, Kenneth D.
N1 - Funding Information:
We thank D. Schankler for use of unpublished data, G. Winterfeld, P. Robinson, G. F. Gunnell, T. M. Bown, K. C. Beard, and R. K. Stucky for information about fossil localities and specimens, A. E. Chew for access to biostratigraphic data, K. E. Jones for advice on vertebral anatomy and allocation, and V. DeLeon for general assistance. Thanks also to J. Galkin and C. M. Mehling (AMNH), P. D. Gingerich and G. F. Gunnell (UM), C. Norris and D. Brinkman (YPM), and A. Tabrum and K. C. Beard (CMNH) for loan of specimens and casts, and to K. C. McKinney for access to Hanley''s field notes. W. von Koenigswald and G. Gruber provided access to and information on Buxolestes specimens. W. von Koenigswald and G. F. Gunnell provided helpful comments on the manuscript. We are grateful to the National Geographic Society and the National Science Foundation (grants BSR-8215099, BSR-8500732, DEB-8918755, IBN-9419776, EAR-0000941, and EAR-0616376, to KDR; and EAR-0739718 to A.E. Chew) for support of field work resulting in the collection of many of the specimens reported here. Fossils were collected under Bureau of Land Management permits, most recently #183-WY-PA95 to KDR.
Publisher Copyright:
Copyright © 2015, The Paleontological Society.
PY - 2015/7/1
Y1 - 2015/7/1
N2 - Species-level diversity and evolution of Palaeosinopa from the Willwood Formation of the Bighorn Basin is reassessed based on substantial new material from the Bighorn, Powder River, and Wind River basins. We recognize three species of Palaeosinopa in the Willwood Formation of the Bighorn Basin: P. lutreola, P. incerta, and P. veterrima. The late Wasatchian species P. didelphoides is not present in the Bighorn Basin. The Willwood species can be differentiated based only on size. P. veterrima is the most common and wide-ranging species and is the most variable in size and morphology: the stratigraphically lowest individuals are smaller, with narrower, more crestiform lower molars; whereas the highest are larger, with wider, more bunodont teeth. Although it could be argued that these represent distinct species, we demonstrate that this morphological evolution occurred as the gradual and mosaic accumulation of features, suggesting in situ anagenetic evolution. The two smaller species are present only low in the section (biochrons Wa0-Wa4) and show no discernable evolution in size or morphology. A new skeleton of Palaeosinopa veterrima from the Willwood Formation is described, and other new postcrania are reported. The skeleton is the oldest associated skeleton of Palaeosinopa known, yet it is remarkably similar to those of younger, more derived pantolestids, the primary disparities being minor differences in proportions of the innominate, femur, and tibia, and co-ossification of the distal tibia and fibula. Either P. incerta or P. lutreola was likely the ancestral population that gave rise to the other Wasatchian Palaeosinopa. Alternatively, P. veterrima may have migrated into the Bighorn Basin from the Powder River Basin.
AB - Species-level diversity and evolution of Palaeosinopa from the Willwood Formation of the Bighorn Basin is reassessed based on substantial new material from the Bighorn, Powder River, and Wind River basins. We recognize three species of Palaeosinopa in the Willwood Formation of the Bighorn Basin: P. lutreola, P. incerta, and P. veterrima. The late Wasatchian species P. didelphoides is not present in the Bighorn Basin. The Willwood species can be differentiated based only on size. P. veterrima is the most common and wide-ranging species and is the most variable in size and morphology: the stratigraphically lowest individuals are smaller, with narrower, more crestiform lower molars; whereas the highest are larger, with wider, more bunodont teeth. Although it could be argued that these represent distinct species, we demonstrate that this morphological evolution occurred as the gradual and mosaic accumulation of features, suggesting in situ anagenetic evolution. The two smaller species are present only low in the section (biochrons Wa0-Wa4) and show no discernable evolution in size or morphology. A new skeleton of Palaeosinopa veterrima from the Willwood Formation is described, and other new postcrania are reported. The skeleton is the oldest associated skeleton of Palaeosinopa known, yet it is remarkably similar to those of younger, more derived pantolestids, the primary disparities being minor differences in proportions of the innominate, femur, and tibia, and co-ossification of the distal tibia and fibula. Either P. incerta or P. lutreola was likely the ancestral population that gave rise to the other Wasatchian Palaeosinopa. Alternatively, P. veterrima may have migrated into the Bighorn Basin from the Powder River Basin.
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U2 - 10.1017/jpa.2015.31
DO - 10.1017/jpa.2015.31
M3 - Article
AN - SCOPUS:84959370801
SN - 0022-3360
VL - 89
SP - 665
EP - 694
JO - Journal of Paleontology
JF - Journal of Paleontology
IS - 4
ER -