Effigia
A toothless, bipedal crocodile relative from the Late Triassic.
Effigia is an extinct genus from the Late Triassic of New Mexico, in the southwestern United States. It belongs to the shuvosaurid family, a group that walked on two legs, had long necks, and toothless, beaked skulls. These features made Effigia and other shuvosaurids look a lot like the 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 only known fossil of Effigia was collected in 1947 by Edwin H. Colbert during an excavation at the Whitaker Quarry of Ghost Ranch, near Abiquiu, New Mexico. Colbert’s team was focused on recovering fossils of the early theropod dinosaur *Coelophysis* and thought no other large vertebrates were in the quarry. Because of this, most of the plaster jackets shipped to the American Museum of Natural History went unopened. The jacket containing the Effigia holotype was finally opened in 2004 by graduate student Sterling Nesbitt, who was looking for more *Coelophysis* specimens. Recognizing the remains were not a dinosaur, Nesbitt tracked down the other blocks from that part of the quarry. He and Mark Norell named the species *Effigia okeeffeae* in January 2006, after artist Georgia O’Keeffe, who lived at Ghost Ranch for many years.
Effigia is famous for its strong resemblance to ornithomimid dinosaurs. In 2007, Nesbitt’s study showed that Effigia is very similar to *Shuvosaurus* and firmly belongs to the archosaur subgroup Pseudosuchia, the lineage leading to modern crocodilians. This similarity to ornithomimids is an extreme case of convergent evolution. Nesbitt also demonstrated that *Shuvosaurus* and *Chatterjeea* are the same animal, and that they belong to a group called Poposauroidea, which includes *Shuvosaurus* and *Poposaurus*. Within that group, Effigia forms a tighter clade with *Shuvosaurus* and the South American *Sillosuchus*, called Shuvosauridae. In 2007, Lucas and others proposed that “Effigia” was actually the same as “Shuvosaurus,” suggesting the new name *Shuvosaurus okeeffeae*, but Nesbitt has not accepted this.
Looking at Effigia’s jaws, researchers think it was a specialized herbivore that browsed on soft plant material. Its weak jaws and sharp beak suggest it couldn’t handle tough food. Earlier ideas that it pecked for food like ostriches or other
- field
- Paleontology
- known_for
- Extreme convergent evolution with ornithomimid dinosaurs; toothless beaked skull; bipedal stance
- discovered_by
- Edwin H. Colbert (1947); named by Sterling Nesbitt and Mark Norell (2006)
- type_species
- Effigia okeeffeae
- geological_period
- Late Triassic
- location
- New Mexico, south-western USA
Lore & Background
The holotype fossil was collected by Edwin H. Colbert in 1947 during an excavation at the Whitaker Quarry of Ghost Ranch, near Abiquiu, New Mexico. Colbert's expedition aimed to recover fossils of the basal theropod dinosaur Coelophysis, and he believed no other large vertebrates were present. The plaster jacket containing the holotype remained unopened until 2004, when graduate student Sterling Nesbitt at the American Museum of Natural History began preparing it while searching for new Coelophysis specimens. Nesbitt instantly recognized the remains were not a dinosaur and tracked down the rest of the blocks from that area. Nesbitt and Mark Norell named it Effigia okeeffeae in January 2006 after artist Georgia O'Keeffe, who spent many years at Ghost Ranch.
Reader's Guide
Effigia is significant for its remarkable similarity to ornithomimid dinosaurs, a case of 'extreme' convergent evolution. In 2007, Nesbitt's description demonstrated that Effigia was very similar to Shuvosaurus and is definitely a member of the archosaur subgroup Pseudosuchia, the line leading towards modern crocodilians. Nesbitt also showed that Shuvosaurus was the same animal as Chatterjeea and that Effigia belongs to an exclusive clade (Shuvosauridae) with Shuvosaurus and the South American Sillosuchus. A 2007 proposal by Lucas and others to synonymize Effigia with Shuvosaurus as 'Shuvosaurus okeeffeae' has not been accepted by Nesbitt. Examination of Effigia's jaws suggests it was a specialist herbivore that browsed on softer plant material, with weak jaws and a sharp beak. Biomechanical studies have estimated that its skull could not withstand the forces of pecking for food like ostriches or other ratites.
Did You Know?
- Effigia was collected in 1947 but its plaster jacket was not opened until 2004.
- It was named after artist Georgia O'Keeffe, who spent many years at Ghost Ranch.
- Effigia is a pseudosuchian, meaning its closest living relatives are crocodilians.
- Its similarity to ornithomimid dinosaurs is considered a case of 'extreme' convergent evolution.
More in Extinct Archosaurs 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record