The rising sun adds a warm ambience to the crisp morning. The forest wakes from its slumber as its inhabitants begin a chorus which will last until the evening. Yet this tune lacks the happy calls of birds, which do not yet exist. Their ancestors do, however, live in these woods, and just like the sun at dawn, they themselves are rising in stature among the trees.
Among the bird relatives present in these ancient Early Jurassic woodlands are podokesaurs. These nimble predators, which can reach 10 feet in length, are a common site. Males of this species produce a distinct grumbling sound using a bright-blue colored throat sac. Females, which usually are larger then males, bear brown, black, and gold scales.
Podokesaurs are social animals, and form large flocks during the wet season when food is plentiful. In this way, they are able to coexist and find mates will little difficulty. Males rarely engage in physical confrontation to win over females. Instead, each male tries to produce a grumble louder than their competitor. The victor wins over the female, and the loser must look somewhere else for a mate. During the dry season, podokesaurs roam in small family groups composed of a mating pair and their offspring. Podokesaur chicks instinctively ride on their parents backs during long journeys, and only start to walk for long periods of time themselves when they are around a year old. The goal of these “dry-season treks” is to find an area where water is still present, which is extremely hard to do given that the podokesaurs live in the rift valleys of the Early Jurassic Northeastern United States. Here, sun beams stab at the gaunt cliffs and flat woodlands that the podokesaurs live in, cracking the ground and burning the trees.
The wet season brings monsoons, and a single one of these can cause widespread flooding and rockslides, which can wipe a valley bare of trees and animals. For those which survive this natural lottery, the monsoons bring much-needed water to parched rivers and lakes. In a single day, a dusty grove of conifers can turn into a bog, and a clearing into a delta. The podokesaurs exploit this, using their long necks to sneak up on and grab invertebrates and fish, such as the coelacanth Diplurus. They are joined by prosauropods like Anchisaurus and larger carnivorous dinosaurs like Eubrontes. In some cases, podokesaurs mob an unlucky prosauropod, causing death by bloodloss and exhaustion. However, the podokesaurs must be wary, as their prosauropod contemporaries are armed with hand spikes which can sever arteries and pierce eyes.
The vast flocks of podokesaurs which form during the wet season are also an omen of death for some. Often, a podokesaur is trampled by others of its kind, and left to die on the side of a riverbed. Now, the skeletons of these fallen predators are being discovered, and provide a glimpse into their incredibly interesting lives.
Podokesaurus holyokensis is an enigmatic species of small carnivorous dinosaur from the Early Jurassic of the Eastern United States. Originally described by Mignon Talbot in 1911 (Talbot, 1911), and has been classified as a coelophysoid dinosaur (Tykoski & Rowe, 2004). In fact, Mignon would be the first woman to describe a non-avian dinosaur (Turner, Burek, & Moody, 2010). Podokesaurus means “swift-footed lizard”, a name fitting for a small, gracile theropod dinosaur. Like other coelophysoids, Podokesaurus was a predator of small animals, preying on anything it could fit into its mouth. Podokesaurus was most likely also a scavenger, feeding on the kills of larger Connecticut Valley predators such as the large theropod dinosaur Eubrontes giganteus (=Dilophosaurus?).
Cast of the holotype of Podokesaurus holyokensis on display at the Peabody Museum. Photo by the author, 2015.
Although the holotype of Podokesaurus suggests that it was an extremely small theropod at only 3 feet in length and 1 foot in height, a second referred specimen (MOS 2001.248) has bones which are around three times longer then the holotype, suggesting an animal around 9 feet long and 3 feet tall. The animal would have lived during the Pliensbachian and Toarcian stages of the Early Jurassic epoch, as the boulder containing the holotype specimen likely originated from a Portland Formation outcrop in Massachusetts. The second referred specimen hails from Connecticut (which may or may not have influenced me to write about this animal) and was described in 1958 (Colbert & Baird, 1958). Footprints of the ichnogenus Grallator are common throughout the Connecticut Valley, and some of them might belong to Podokesaurus or something very much like it, providing a glimpse into the locomotion and behavior of this theropod dinosaur taxon.
Footprints from the Connecticut Dinosaur trackways. In Green: Grallator
In Purple: Anomoepus In tan: Batrachopus. Photo by the author, 2015.
In the Portland Formation environment, Podokesaurus would have coexisted with a menagerie of other dinosaurs and reptiles, including the prosauropods Anchisaurus and Ammosaurus (Weishampel et al., 2004), as well as the large theropod dinosaur Eubrontes (Dalman, 2012). This formation provides one of the best glimpses we have of the rift valley ecosystems of the Early Jurassic Northeastern US.
Eubrontes giganteus footprint cast. Photo by the author, 2015.
Not only has Podokesaurus extensively furthered our knowledge the dinosaurs of the Eastern US, but the citation of the paper describing it also showcases the name of the first woman to ever describe a non-avian dinosaur (keep in mind that Podokesaurus was described in 1911, almost a decade before the events of 1919-20 which finally allowed women to vote in the United States). In this way, Podokesaurus not only becomes an important animal in understanding the paleoecology of Early Jurassic ecosystems, but also an animal which represents a key time in American history.
Podokesaurus holyokensis by the author. Pencils on paper, 2015.
For those who want to see some of the footprints found in the Connecticut Valley, the footprint slab showcased above is now on display at the Stamford Museum. For directions and more information, go to http://www.stamfordmuseum.org
References
1. Talbot, M. 1911. “Podokesaurus holyokensis, a new dinosaur of the Connecticut Valley.“ American Journal of Science 31: 469-479.
2. Tykoski, R.S. & Rowe, T. 2004. “Ceratosauria.” In Weishampel, D.B., Dodson, P., & Osmolska, H. (eds.) The Dinosauria (2nd Edition). Berkeley: University of California Press. pp. 47–70.
3. Turner, S.; Burek, C.; Moody, R.T. 2010. “Forgotten women in an extinct Saurian ‘mans’ World.” In Moody, R.T.; Buffetaut, E.; Martill, D.; Naish, D. (eds.) Dinosaurs and Other Extinct Saurians: A Historical Perspective. The Geological Society of London Special Publication 343: 111-153.
4. Colbert, E.H. & Baird, D. 1958. “Coelurosaur bone casts from the Connecticut Valley Triassic.” American Museum Novitates 1901: 1-11.
5. Weishampel, D. B. et al. 2004. “Dinosaur distribution (Early Jurassic, North America).” In Weishampel, D. B.; Dodson, P.; and Osmólska, H. (eds.): The Dinosauria (2nd Edition) Berkeley: University of California Press. pp. 530–532.
6. Dalman, S. G. 2012. “New Data on Small Theropod Footprints from the Early Jurassic (Hettangian) Hartford Basin of Massachusetts, United States.” Bulletin of the Peabody Museum of Natural History 53(2): 333-353.
An Odyssey of Time 