| Pectinodon | |
|---|---|
 | |
| Tooth of cf.Pectinodon | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Troodontidae |
| Genus: | †Pectinodon Carpenter, 1982 |
| Type species | |
| †Pectinodon bakkeri Carpenter, 1982 | |
| Synonyms | |
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Pectinodon is agenus oftroodontidtheropoddinosaurs from the end of theMaastrichtian age of theLate Cretaceous period (66 mya). It currently contains a single validspecies,Pectinodon bakkeri (sometimes classified asTroodon bakkeri), known only from teeth.[1]
In 1982,Kenneth Carpenter named a number of theropod teeth from the late Maastrichtian agedLance Formation ofWyoming as thetype speciesPectinodon bakkeri. The generic name is derived from theLatin wordpecten, meaning "comb", and the Greek word ὀδών,odon, meaning "tooth", in reference to the comb-like serrations on the rear edge of the teeth. Thespecific name honors famed paleontologistRobert Thomas Bakker.[1]
The holotype, UCM 38445, consists of a 6.2 mm long adult tooth. Theparatypes are three juvenile teeth.[1]
In 1985,Lev Nesov named a second species,Pectinodon asiamericanus, based on specimen CCMGE 49/12176, a tooth from theKhodzhakul Formation ofUzbekistan that dates from theCenomanian age.[2] This is today often considered anomen dubium.[3]
While historically considered synonymous withTroodon or more specifically the speciesTroodon formosus,Philip Currie and colleagues (1990) noted that theP. bakkeri fossils from theHell Creek Formation and Lance Formation might belong to different species. In 1991, George Olshevsky assigned the Lance formation fossils to the speciesTroodon bakkeri.[4][5] In 2011, Zanno and colleagues reviewed the convoluted history of troodontid classification in Late Cretaceous North America. They followed Longrich (2008) in treatingPectinodon bakkeri as a valid genus[6] and noted that it is likely the numerous Late Cretaceous specimens currently assigned toTroodon formosus almost certainly represent numerous new species, but that a more thorough review of the specimens is required.[7]
In 2013, Currie andDerek Larson concluded thatPectinodon bakkeri was valid and its teeth could be found both in the Lance Formation and the coeval Hell Creek Formation. Some teeth from the olderCampanianDinosaur Park Formation could not be statistically differentiated from them, likely due to an insufficiently large sample, and were referred tocf. Pectinodon.[8]
WhilePectinodon is only known from teeth, its larger family Troodontidae is known from much more complete specimens. They were small, bird-like feathered bipedalmaniraptorans with proportionally large eyes and brains. Likedromaeosaurids, they possessed a "sickle-claw" on the second toe of each foot. See theTroodontidae article for more information.
Pectinodon's eponymous teeth are generally small (< 1 cm crown height) labio-lingually compressed, exhibit basal constriction, and possess large, triangular, apically-oriented denticles on the distal edge. The holotype tooth has pitting on the lingual surface and no denticles on the mesial carina,[1] though other specimens are known to have fine serrations near the base of the crown on the mesial carina.[9]
Despite having only teeth to infer behavior forPectinodon, they are very informative fossils. Several studies have been done on troodontid teeth, shedding light on their behavior and ecology. Their toothmorphology suggests they preferred soft prey items like invertebrates, small vertebrates, or carrion. Their dentition was not as well suited for high-stress feeding as in their cousins the dromaeosaurids andtyrannosaurids.[10] Tooth morphology also led some researchers to speculate that troodontids wereomnivorous.[11] This hypothesis was reaffirmed in a study that used stable isotopes in tooth enamel to reconstruct paleo-ecologies.[12]
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