Zapsalis

''Zapsalis'' is a genus of dromaeosaurine theropod dinosaurs. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include teeth but no other remains.

Etymology

The generic name is derived from Greek ''za~'', "thorough", and ''psalis'', "pair of scissors". The specific name means "abrading" in Latin.

History and classification

Fossils of ''Zapsalis'' were first described by American paleontologist Edward Drinker Cope in 1876 but as species of the large carnivorous theropod ''Laelaps'' (now ''Dryptosaurus'').Cope, E. D. (1876). Descriptions of some vertebrate remains from the Fort Union beds of Montana. ''Proceedings of the Academy of natural Sciences of Philadelphia'', 248-261. Cope erected 2 species, ''Laelaps explanatus'' and ''L. laevifrons'', the former based on a collection of 27 teeth and the latter based on a single tooth. It wasn't until later in 1876 that Cope made the genus ''Zapsalis'', with ''Z. abradens'' as the type, based on a second premaxillary tooth.Cope, E. D. (1876). On some extinct reptiles and Batrachia from the Judith River and Fox Hills beds of Montana. ''Proceedings of the Academy of natural Sciences of Philadelphia'', 340-359. All of the fossils were collected from the Campanian age strata of the Judith River Formation in Montana, USA. Cope named ''Zapsalis'' during the Bone Wars, his competition with Yale paleontologist Othniel Charles Marsh, to collect and describe as many fossil taxa as possible.

After the Bone Wars, the type fossils of ''Zapsalis'' and the ''Laelaps'' species were sold to the American Museum of Natural History in New York. In the wake of the Bone Wars, the complicated errors in dinosaur taxonomy were left to other paleontologists, with the ''Laelaps'' species being moved to other theropod dinosaurs like ''Deinodon,'' ''Aublysodon,'' and ''Dromaeosaurus''.Matthew, W. D., & Brown, B. (1922). The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta. Bulletin of the AMNH; v. 46, article 6. ''Z. abradens'' was moved to ''Dromaeosaurus'' and synonymized with the other Dromaeosaur ''Paronychodon.'' It wasn't until 2002 that Julia Sankey e.a. concluded the teeth represented a separate "''?Dromaeosaurus'' Morphotype A". In 2013 Derek Larson and Philip Currie recognised ''Zapsalis'' as a valid taxon from the Judith River and Dinosaur Park Formation. The teeth are typified by a combination of rounded denticles, straight rear edge and vertical grooves. Similar teeth from the older Milk River Formation were referred to a ''cf. Zapsalis''. In 2019, Currie and Evans announced that the ''Zapsalis'' teeth from the Dinosaur Park Formation represented the second premaxillary tooth of ''Saurornitholestes langstoni'', in a paper describing a complete skull of that species. The authors kept the species distinct because the type species' holotype is likely indeterminate on a species level.

As for ''Laelaps explanatus'' and ''L. laevifrons,'' they were never synonymized with ''Zapsalis'' but have been synonymized with ''Saurornitholestes langstoni'' and in turn, ''Zapsalis,'' as well.

Description

The type tooth of ''Z. abradens'' is flat lingually, with no mesial serrations and 3 distal serrations per millimeter and is 12 mm in total length. There are three lingual ridges and four labial ones. Currie & Evans, 2019 diagnosed ''Zapsalis'' from ''Saurornitholestes'' by noting the type of the former is lacking mesial serrations and being concave apicodistally, and therefore "recommended that the two genera be kept separate." The second premaxillary teeth of ''Zapsalis'' and other dromaeosaurids may have been structurally specialized for preening feathers, as seen in some Oviraptorosaurs as well.

Paleoenvironment

All 4 named species are known from the Judith River Formation, the site of expeditions first by Edward Drinker Cope's crews during the early stages of the Bone Wars, including the discoveries of many taxa that he named, though all are now seen as dubious. These include fossils of large, carnivorous tyrannosaurid theropods like ''Aublysodon'' and ''Deinodon.'' As for the herbivorous Ornithischians, like the beaked hadrosaurids ''Trachodon'' and ''Cionodon'' were named. The most common fossils are those of the horned Ceratopsians like ''Monoclonius, Ceratops,'' and '' Pteropelyx.'' Lastly, the armored ankylosaur ''Palaeoscincus'' is known from scattered teeth.Cope, E.D. (1879). Hayden, F.V. (ed.). "The Relations of the Horizons of Extinct Vertebrata". ''United States Geological and Geographical Survey''. 5 (1): 37–38.

See also

* Timeline of dromaeosaurid research

References

{{Taxonbar, from=Q2306005

Eudromaeosaurs
Late Cretaceous dinosaurs of North America
Fossil taxa described in 1876
Taxa named by Edward Drinker Cope
Paleontology in Montana
Paleontology in Alberta
Campanian genus first appearances
Campanian genus extinctions