Effigia

Credit: AMNH on Twitter.

*Effigia* is an extinct genus of pseudosuchian archosaur that lived in Mexico during the Late Triassic.

## History

*Effigia*, first found by Edwin H. Colbert in Ghost Ranch Quarry, was 2 meters (6 feet, 7 inches) upon discovery and excavated from 1947-1948. However, Colbert did not think large vertebrates were present besides theropod dinosaurs, so did not bother to open the jackets after they were sent to the American Museum of Natural History. In January 2006, Sterling Nesbitt started to open the jackets in hopes of finding new *Coelophysis*. At this point, Nesbitt had started in his PhD career, and had started a project on Triassic dinosaurs. Before this event, the jackets had remained untouched. However, he found *Effigia*; realizing it was non-dinosaurian and found more blocks from the same quarry. This block was encased in plaster but partially prepared, from 1947, so it had to remain on the storage shelves where it would be studied. Nesbitt and Mark Norell named it *E. okeeffeae* the same month, after Georgia O'Keeffe, who spent many years at Ghost Ranch. The genus name is Latin for "ghost", after Ghost Ranch. *Effigia* was extremely popular in media, making international headlines. This inspired Steve Brusatte's career, who had seen its impact in the news.

## Description

*Effigia* has slender morphology similar to *Struthio* and *Ornithomimus* with large orbits, an edentulous beak, a downturned jaw and a flat skull roof. This had led to ecological comparisons with the latter 2 genera that are generally considered untrue. Effigia has small arms and ankle morphology near identical to crocodiles.

## Classification

*Effigia* is very similar to ornithomimids. Besbitt (2007) notes it is also very similar to *Shuvosaurus*, but is definitively a suchian, having extreme convergent evolution. Nesbitt also finds *Shuvosaurus* is synonymous with *Chetterjeea*, belonging to a clade containing related suchians, such as *Poposaurus* and *Effigia*. Within, *Effigia* forms a more exclusive clade with *Shuvosaurus* and *Silosuchus*. Lucas et al. (2007) suggests it is synonymous with *Shuvosaurus*, naming "S. okeefeae". This change has not taken place since.

## Paleobiology

A 2021 biomechanics study performs several tests on the crania of *Effigia* and close taxa. They find a weak mandible that was limited to the anterior of the jaw and limited convergent function with *Ornithomimus* and *Struthio*. They interpret this as *Effigia* being a specialist herbivore that fed on soft vegetation, such as ferns. It used it's beak to shear plants. *Effigia* likely had a weak bite, and did not peck feed like *Struthio* do.

*Effigia* was very dinosaur-like, but is clearly a pseudosuchian. Data indicates this group was very widespread during the time of *Effigia*. Pseudosuchians like *Effigia* may demonstrate how the dinosaurs rose to power later in the Mesozoic.

## References

* https://en.wikipedia.org/wiki/Effigia
* https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.24827
* https://paleobiodb.org/classic/basicTaxonInfo?taxon\_no=70614
* https://www.chapters.indigo.ca/en-ca/books/the-rise-and-fall-of/9780062490438-item.html