Abstract
A comprehensive description of the holotype skeleton is presented here for the first time of the lower Permian (Artinskian) reptile Eudibamus cursoris from the Bromacker locality of Germany since the brief description of the holotype in 2000. The holotype is essentially complete and is the only known bolosaurid represented by a well-preserved articulated skeleton. Included in the description here is a superbly preserved, partial, articulated second specimen of E. cursoris discovered at the same locality that includes a short portion of the vertebral column associated with the pelvis and right hindlimb. Descriptions of the holotype and new specimen add substantially to features of the skull and postcranium that not only confirm a bolosaurid assignment, but also add significantly to an already long list of structural features supporting an ability unique among Paleozoic vertebrates to reach relatively high bipedal and quadrupedal running speeds employing a parasagittal stride and digitigrade stance with the limbs held in a near vertical posture. Structural differences between the two specimens are restricted to the tarsi and are attributed to different ontogenetic stages of ossification, with the holotype representing a more juvenile individual, and the larger second specimen representing a more mature animal.
Highlights
Bolosauridae was first formally proposed by Cope in 1878 to include the sole representative Bolosaurus striatus Cope, 1878, which was based on several poorly preserved skulls, jaw fragments, and a few postcranial fragments, all recovered from a single lower Permian locality in Texas
Eudibamus cursoris is truly a unique reptile for its times. Is it among the few oldest known bipedal reptiles, it is the oldest known late Paleozoic reptile capable of achieving relatively high running speeds during quadrupedal and bipedal locomotion. This was accomplished by uniquely employing a parasagittal stride and digitigrade posture with the limbs positioned in a near vertical stance beneath the trunk and swung fore and aft in a pendulum-like style
The possession of the unique locomotor adaptations by E. cursoris as early as the lower Permian raises the very plausible narrative that undiscovered terrestrial reptiles of approximately the same age may not have been restricted to a sprawling quadrupedal locomotion style in their early history
Summary
Bolosauridae was first formally proposed by Cope in 1878 to include the sole representative Bolosaurus striatus Cope, 1878, which was based on several poorly preserved skulls, jaw fragments, and a few postcranial fragments, all recovered from a single lower Permian locality in Texas. The laterally exposed left prefrontal appears to be essentially complete and preserved in proper orientation within the skull and relative to surrounding elements It consists of a narrow longitudinally elongated base with a horizontally straight ventral margin, which likely contacted the dorsal margin of the anterior half of the ventrally displaced lacrimal. The ilia in the holotype are complete and occupy their correct relationship with the sacrum but appear to be barely disarticulated from the sacral transverse processes In both the holotype and referred specimen MNG 12895 the typical broad dorsal iliac blade is absent and in its place elongated anterior and posterior processes of subequal lengths unite above the acetabulum in a narrow band with an uninterrupted horizontal dorsal margin. In a sprawling posture the force of the hindlimb is directed medially and is far less effective in supporting the weight of the trunk than if contained in a vertical parasagittal plane position beneath the trunk
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