Effigia
A toothless, bipedal crocodile relative from the Late Triassic.
Effigia is an extinct genus of shuvosaurid from the Late Triassic of New Mexico, in the southwestern United States. It stood on two legs, had a long neck, and a toothless, beaked skull. Because of these features, Effigia and other shuvosaurids looked a lot like ornithomimid dinosaurs from the Cretaceous. But shuvosaurids were not dinosaurs. They were a specialized family within the poposauroid pseudosuchians, meaning their closest living relatives are crocodilians.
The holotype fossil was collected in 1947 by Edwin H. Colbert, who was leading an excavation at the Whitaker Quarry of Ghost Ranch, near Abiquiu, New Mexico. Colbert’s team was there to recover abundant fossils of the basal theropod dinosaur *Coelophysis*, and he thought no other large vertebrates were in the quarry. As a result, the crew did not open the plaster jackets of most blocks shipped to the American Museum of Natural History. The jacket containing the *Effigia* holotype was not prepared until 2004, when graduate student Sterling Nesbitt uncovered the specimen at the AMNH while opening jackets to find more *Coelophysis*. Nesbitt immediately recognized the remains were not from a dinosaur and tracked down the other blocks from that quarry area. In January 2006, Nesbitt and curator Mark Norell named the species *Effigia okeeffeae* after Georgia O’Keeffe, who spent many years at Ghost Ranch.
*Effigia* is notable for its strong resemblance to ornithomimid dinosaurs. In 2007, Nesbitt’s description showed that *Effigia* was very similar to *Shuvosaurus* and is definitely a member of the archosaur subgroup Pseudosuchia, the line leading to modern crocodilians. This similarity to ornithomimids is an example of extreme convergent evolution. Nesbitt also showed that *Shuvosaurus* was the same animal as *Chatterjeea* and belonged to a group of closely related suchians called Poposauroidea, which includes *Shuvosaurus* and *Poposaurus*. Within that group, *Effigia* forms an even tighter clade with *Shuvosaurus* and the South American *Sillosuchus*, called Shuvosauridae. In 2007, Lucas and others suggested *Effigia* was synonymous with *Shuvosaurus* and proposed the new combination *Shuvosaurus okeeffeae*, but Nesbitt has not accepted this.
Examination of *Effigia*’s jaws suggests it was a specialist herbivore that browsed on softer plant material, because its jaws were weak and its beak was sharp. It was once thought to have pecked for food like ostriches or other ratites, but biomechanical studies estimate its skull could not withstand such forces.
- field
- Paleontology
- known_for
- Extreme convergent evolution with ornithomimid dinosaurs; toothless beaked skull; bipedal stance
- type_species
- Effigia okeeffeae
- geological_period
- Late Triassic
- location
- New Mexico, south-western USA
Lore & Background
Effigia was a bipedal reptile with a long neck and a toothless, beaked skull, giving it a striking resemblance to the ornithomimid dinosaurs of the Cretaceous. However, it was not a dinosaur; it belonged to the Pseudosuchia, the lineage that includes modern crocodilians. Its similarity to ornithomimids is considered an extreme example of convergent evolution. The animal was a specialist herbivore, using its sharp beak to browse on softer plant material. Its jaws were relatively weak, and biomechanical studies indicate its skull could not withstand the forces involved in pecking for food, as ostriches do. Effigia is known from the Late Triassic of New Mexico in the southwestern United States. Its remains were discovered in the Whitaker Quarry at Ghost Ranch, near Abiquiu. The holotype fossil was collected in 1947 by an expedition led by Edwin H. Colbert, who was primarily searching for the dinosaur Coelophysis and believed no other large vertebrates were present in the quarry. The specimen remained unopened in its plaster jacket until 2004, when it was prepared and recognized by graduate student Sterling Nesbitt. He identified it as a non-dinosaur and located additional blocks from the same quarry area. Effigia is closely related to Shuvosaurus and Sillosuchus within the family Shuvosauridae, a specialized group of poposauroid pseudosuchians.
Reader's Guide
Effigia is significant for its remarkable similarity to ornithomimid dinosaurs, a case of 'extreme' convergent evolution. Nesbitt also showed that Shuvosaurus was the same animal as Chatterjeea and that Effigia belongs to an exclusive clade within Poposauroidea, forming an even more exclusive clade with Shuvosaurus and the South American Sillosuchus (Shuvosauridae). Examination of Effigia's jaws suggests it was a specialist herbivore that filled a niche as a browser feeding on softer plant material, due to its weak jaws and sharp beak. It was previously suggested that it pecked for food like ostriches, but biomechanical studies have estimated that its skull could not withstand such forces.
Did You Know?
- Its closest living relatives are crocodilians, despite its dinosaur-like appearance.
- The species name okeeffeae honors artist Georgia O'Keeffe, who spent many years at Ghost Ranch.
- Effigia's similarity to ornithomimid dinosaurs is considered a case of 'extreme' convergent evolution.
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