Habrosaurus Temporal range: 84.9–58.7 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Illustration of Habrosaurus dilatus specimen UALVP 43910
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Urodela
Family:	Sirenidae
Genus:	†Habrosaurus Gilmore, 1933
Type species
†Habrosaurus dilatus Gilmore, 1933
Other species
†Habrosaurus prodilatus Gardner, 2003
Synonyms
Adelphesiren[1]

Habrosaurus (IPA: [hæbroʊsʊrʌs], meaning "graceful lizard") is an extinct genus of prehistoric salamanders, and the oldest known member of the family Sirenidae. Two species are known, H. prodilatus from the middle Campanian Dinosaur Park Formation of Alberta,^[1] and H. dilatus from the late Maastrichtian and Paleocene of western North America. It is relatively common in the Lance Formation of Wyoming, and less common in the Hell Creek Formation of Montana.

Habrosaurus was a gigantic sirenid,^[2] its length is estimated to be around 1.6 m (5 ft 3 in), estimated from its trunk vertebrae length (up to 2 cm long).^[3] H. prodilatus possessed chisel-like teeth, while H. dilatus had bulkier crowns. The teeth of H. dilatus also exhibited heavy wear facets while those of H. prodilatus had only mild wear, suggesting that H. dilatus was more adapted for durophagy than H. prodilatus. H. dilatus may have preyed upon arthropods with hard carapaces as well as mollusks.^[1]

Habrosaurus is a sister taxa to both Pseudobranchus and Siren^[1] which are the only genera in the family Sirenidae. Sirenids are classified by their neotenous traits (complete lack of hindlimbs and external gills in both larval and adult states).

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