Podokesaurus is a genus of coelophysoid dinosaur that lived in what is now the eastern United States during the Early Jurassic Period. The first fossil was discovered by the geologist Mignon Talbot near Mount Holyoke, Massachusetts, in 1910. The specimen was fragmentary, preserving much of the body, limbs, and tail. In 1911, Talbot described and named the new genus and species Podokesaurus holyokensis based on it. The full name can be translated as "swift-footed lizard of Holyoke". This discovery made Talbot the first woman to find and describe a non-bird dinosaur. The holotype fossil was recognized as significant and was studied by other researchers, but was lost when the building it was kept in burned down in 1917; no unequivocal Podokesaurus specimens have since been discovered. It was made state dinosaur of Massachusetts in 2022. Estimated to have been about 1 m (3 ft) in length and 1–40 kg (2–90 lb) in weight, Podokesaurus was lightly constructed with hollow bones, and would have been similar to Coelophysis, being slender, long-necked, and with sharp, recurved teeth. The vertebrae were very light and hollow, and some were slightly concave at each end. The cervical (neck) vertebrae were relatively large in length and diameter compared to the dorsal (back) vertebrae, and the caudal (tail) vertebrae were long and slender. The humerus (upper-arm bone) was small and delicate, less than half the length of the femur (thigh-bone). The pubis (pubic bone) was very long, expanding both at the front and hind ends. The femur was slender, nearly straight, had thin walls, and was expanded at the back side of its lower end. The three metatarsals of the lower leg were closely appressed together forming a compact structure. Since it was one of the few small theropods known at the time it was described, the affinities of Podokesaurus were long unclear. It was placed in the family Podokesauridae along with other small theropods, and was speculated to have been similar to a proto-bird. It was suggested it was a synonym of Coelophysis and a natural cast specimen was assigned to it, but these ideas are not currently accepted. The family Podokesauridae is not in use anymore, having been replaced by Coelophysidae, and Podokesaurus is thought to have been a coelophysoid. As such, Podokesaurus would have been a fleet-footed predator, with powerful forelimbs and grasping hands. It is estimated it could have run at 15–20 km/h (9–12 mph). Podokesaurus is thought to have been collected from the Portland Formation, the age of which has long been unclear, but is currently believed to date to the Hettangian–Sinemurian stages of the Early Jurassic, between 201 and 190 million years ago.
Discovery and history
In 1910, the American geologist Mignon Talbot was walking with her sister Ellen to Holyoke, Massachusetts, in the eastern US, when they passed a farm and noticed a small hill nearby. It had a gravel pit at one side, and was formed by an accumulation of sand, gravel, and boulders left by a receding glacier. Talbot noticed a white streak on a sandstone boulder at the bottom of the gravel pit, and upon discovering these were bones, she told her sister she had found a "real live fossil". This was because many fossil tracks had previously been discovered in the Connecticut Valley (that she had often taken her students to see), but few actual dinosaur skeletons, and none at Mount Holyoke. She was granted permission by the land owner to collect the specimen for Mount Holyoke College (an all-women's college a few miles from there), where she was head of the geology department. The next day she brought a group of workmen to collect the specimen, and found another piece of sandstone that contained the rest of the fossil as well as impressions of those in the first slab. The specimen appeared to have been exposed for years with no one noticing it, the boulder having been broken open by people or frost. The fossil was brought to the laboratory where it was prepared and photographed. The incomplete specimen preserved 5 cervical (neck), 11 dorsal (back) and 24 caudal (tail) vertebrae, a fragment of the left scapula (shoulder blade) and right coracoid (part of the pectoral girdle), a partial left humerus (upper arm bone), phalanx bones of 3 fingers, including 2 unguals (claw bones), ribs, the pubis and ischium (bones forming the lower front and lower back of the pelvis, respectively), the femora (thigh bones), the left tibia (lower leg bone), a fragment of the right astragalus (a bone in the ankle), articulated metatarsals (foot bones) of the left foot, followed by 3 pedal phalanges (toe bones), partial metatarsals and possible phalanges of the right foot, and fragments of uncertain identity. The light and delicate bones were in their natural position or nearly so within the rock, except for the tail and uncertain fragments, which were a few centimeters away from the skeleton, following a long gap in the skeleton behind the pelvis. The front half of the neck was missing.
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