Convergent Evolution Among Reptiles – part 2

Yesterday we looked at part 1 of convergence among reptiles. Today we’ll add a few other examples from the large reptile tree.

Silesaurus and dinosaurs: Both developed a bipedal configuration without a calcaneal tuber. All other poposaurs have a tuber. In addition, ornithischian dinos shared a predentary with Silesaurus.

Legless lizards: snakes, legless skinks, legless geckos. It is widely known that these squamate taxa all lose their limbs independently. The origin of snakes  was last covered here with Tetrapodophis.

Finbacks: Spinosaurs, sphenacodonts, Lotosaurus, Arizonasaurus.These diverse taxa all have elongate dorsal spines creating a tall back fin.

Procolophonids and pareiasaurs: These unrelated taxa, Hypsognathus and Anthodon, both developed spiky laterally expanded cheek bones (quadratojugals).

Tetraceratops and basal therapsids: Both of these taxa had enlarged canines and many paleontologists consider Tetraceratops a basal therapsid. According to the large reptile tree, Tetraceratops is related to Tseajaia, which also has smaller canine teeth.

Trioceros and Triceratops: Both of these unrelated taxa developed three facial horns. Trioceros is a chameleon. Triceratops is a dinosaur.

Four clades of pterodactyloid-grade pterosaurs and two other demi-pterodactyloid pterosaurs: Various basal pterosaurs developed pterodactyloid-grade traits. Two dorygnathid taxa evolved into azhdarchids and ctenochasmatids. Two scaphognathid taxa evolved into cycnorhamphids + ornithocheirids and germanodactylids + pterodactyl ids. Wukongopterids developed some, but not all pterodactyloid-grade traits (they retain a long pedal digit 5 and long tail). Anurognathids do likewise (but they retain separate nares and a long pedal digit 5).

Azhdarchid pterosaurs and eopteranodontid pterosaurs: Both of these unrelated clades developed medium to large stork-like forms.

Longisquama and Lemur: Both of these unrelated taxa (Fig. 1) had a small skull with large orbits on a short skull, a long dorsal series, an attenuated tail held aloft, shorter forelimbs and very long leaping hind limbs.

Figure 1. Longisquama (Triassic fenestrasaur) compared to a modern Lemur. Similar body shapes might imply similar locomotory patterns.

Figure 1. Longisquama (Triassic fenestrasaur) compared to a modern Lemur. Similar body shapes might imply similar locomotory patterns. Click to enlarge.

Cartorhynchus, ichthyosaurs, plesiosaurs, certain mosasaurs and sea turtles: Cartorhynchus had large, ichthyosaur-like/plesiosaur-like fore flippers, and small hind flippers, like living sea turtles, but is related to basal pachypleurosaurs, all of which had distinct fingers.

Multiple tooth rows: captorhinids and Azendohsaurus + Trilophosaurus + Rhynchosauria: Developed independently. these taxa had multiple tooth rows developed on the maxilla and palatine.

Hyper-elongate necks: tanystropheids (Fig. 2) and sauropods. Both of these independent clades are famous for their long necks.

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette is 6 feet (1.8m) tall.

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette is 6 feet (1.8m) tall.

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