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 in length and 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 were very light and hollow, and some were slightly concave at each end. The (neck) vertebrae were relatively large in length and diameter compared to the (back) vertebrae, and the (tail) vertebrae were long and slender. The (upper-arm bone) was small and delicate, less than half the length of the (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 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 The family Podokesauridae is not in use anymore, having been replaced by Coelophysidae, and Podokesaurus is thought to have been a coelophysoid.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 . 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 (neck), 11 (back) and 24 (tail) vertebrae, a fragment of the left (shoulder blade) and right (part of the ), a partial left (upper arm bone), of 3 fingers, including 2 (claw bones), ribs, the and (bones forming the lower front and lower back of the pelvis, respectively), the (thigh bones), the left (lower leg bone), a fragment of the right (a bone in the ankle), articulated (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.
The significance of the fossil was confirmed at an intercollegiate meeting of geology departments, and when the American paleontologist Richard Swann Lull subsequently encouraged Talbot to describe the specimen, she replied she did not know anything about dinosaurs, but Lull suggested she should study them and then describe it. In December 1910, Talbot read a preliminary description of the fossil at the Paleontological Society meeting at Pittsburgh, and in June 1911 she published a short scientific description, in which she made the specimen the holotype of the new genus and species Podokesaurus holyokensis. The generic name is derived from the Ancient Greek words podōkēs (), which means "swift (or fleet)-footed", an epithet commonly used in reference to the Greek hero Achilles, and saura () meaning "lizard", while the specific name refers to Holyoke. In full, the name can be translated as "swift-footed lizard of Holyoke". The discovery and naming of Podokesaurus made Talbot the first woman to find and describe a non-bird dinosaur. The American paleontologist Robert T. Bakker stated in 2014 that while old professors grumbled that women were unfit for working with fossils during his time at university, Talbot's discovery of Podokesaurus was a counterargument to that.
By the time the description was published, Talbot had sent the fossil to the Peabody Museum of Natural History at Yale University for further preparation and study, where cast replicas were also made of the bones as they lay in the rock. There, Lull drew a reconstruction of the skeleton, basing the parts missing from the fossil on the equivalents in Compsognathus, and created a model of the animal in life, which Talbot later described as having a "sardonic smile". Lull expanded on Talbot's article in a 1915 publication, wherein he also proposed other identities for some of the bones than what she had originally suggested, including a partial coracoid instead of a scapula and part of the tibia instead of the (part of the hips). Lull suggested that the boulder containing the fossil must have come from a ledge which lay on the south side of the Holyoke Range, about two or three miles north of where it was found, and specified that it was from the Longmeadow Sandstone.
Lull had sent his manuscript to the Danish ornithologist Gerhard Heilmann for criticism prior to publication. Heilmann published his response in a 1913 article in which he included previously unpublished photos of the fossil received from Talbot, as well as his own restorations. He disagreed with some of Lull's anatomical interpretations, and had corresponded regarding the fossil with the American zoologist Robert Wilson Shufeldt about his contentions. Heilmann's article was one in a series about the origin of birds, wherein he examined the skeletons of prehistoric reptiles to find traits that may have been ancestral to birds. In a 1916 Washington Academy of Sciences meeting, Shufeldt gave an account of his correspondence with Lull, Talbot, and Heilmann, and agreed with the latter in some of his criticisms of Lull's restoration of Podokesaurus.
Talbot wanted the fossil to stay at Yale or Washington on permanent exhibit, where it could "be with its kind", but it was kept at Mount Holyoke in the old science building, Williston Hall, as a local specimen, where it became a "pet curiosity" for the students. During the Christmas break of 1917, Williston Hall burned down, and no remains of the Podokesaurus fossil were found in the rubble. The American writer Christopher Benfey pointed out in 2002 that Podokesaurus therefore had the peculiar distinction of being the dinosaur that vanished twice. The German paleontologist Friedrich von Huene was the last to study and describe the holotype specimen, in a 1914 publication before it was destroyed (he had studied it at Yale before Talbot's description was published). While the college's fossil collections were almost entirely destroyed by the fire, its facilities and collections continued to grow and improve afterwards due to Talbot's efforts.
No other unequivocal Podokesaurus specimens have since been found, but cast replicas of the type specimen remain at the Peabody Museum of Natural History and the American Museum of Natural History in New York. Podokesaurus received little further attention until new and abundant fossils of Coelophysis were discovered in the late 1940s, and the anatomy of small theropod dinosaurs became clearer; the American paleontologists Edwin Harris Colbert and Donald Baird compared Podokesaurus with Coelophysis in 1958, using the casts of the former. Along with the sauropodomorph Anchisaurus, Podokesaurus was among the first substantial collections of dinosaur skeletal material known from the East Coast of North America. Apart from a tooth (assigned to Coelophysis in 1976), all other Early Jurassic theropod records on the East Coast are footprints.
In 2021, Podokesaurus and Anchisaurus were proposed as contenders for state dinosaur of Massachusetts by Representative Jack Patrick Lewis, with Podokesaurus winning the online poll. On May 2, 2022, Governor Charlie Baker signed a law making it the official state dinosaur. A 2024 paper about identification of natural dinosaur bone casts concluded that new methods could be used to find additional remains of Podokesaurus, noting its status as state dinosaur.
Description
The preserved body of the only known Podokesaurus fossil was long. Lull estimated the complete length of Podokesaurus to have been , the neck accounting for , the back for , the (the vertebrae of the pelvic region) for , and the tail for . Von Huene estimated the animal to have been long, with the tail accounting for about , more than 1.5 times the rest of the skeleton together. Colbert estimated the animal's length at about . In 1995, the writer Jan Peczkis estimated Podokesaurus to have weighed , through pelvic height determination (based on von Huene's measurements). The paleontologist Gregory S. Paul estimated it to have weighed in 2016 (based on a 1 m length estimate). Talbot stated in 1937 that those scientists who had seen the specimen did not think it was a young individual as there were no indications of cartilage that would turn to bone with age, while Paul thought it was possibly juvenile. In general, the animal was lightly constructed, with hollow bones. As a coelophysoid, it would likely have been similar in build to for example Coelophysis, being slender, long-necked, and with sharp, recurved teeth.