22-13 Teeth through time: mapping Deinonychus paleoecology through the Early Cretaceous using morphometrics

Session: Working Up an Apatite: Teeth as Paleo -Ecological and -Climatological Archives

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Abstract:

Deinonychus is a charismatic and scientifically important taxon in understanding dinosaur-bird evolution; however, few studies have examined morphological differences between specimens from geographically disparate localities, all of which are attributed to the monospecific genus. Recent workers have suggested there may be hidden taxonomic variation within the genus; this study is the first step in ascertaining and assessing this variation. Since limited postcranial material is available, but teeth are abundant, a morphometric study of isolated teeth was conducted to evaluate if differences in tooth morphology exist between the three examined formations - the Arundel in Maryland; the Cloverly in Montana/Wyoming; and the Antlers in Oklahoma.

A total of 51 teeth (Arundel= 7; Cloverly= 19; Antlers= 25) were measured with calipers to obtain discrete measurements of morphologically diagnostic features. Of the 18 measurements taken, or calculated from measured values, 11 were morphologically informative. The morphometric data was analyzed in PAST where a MANOVA test identified a significant difference between the Cloverly-Antlers pair (p=0.048). The other two pairs, Cloverly-Arundel and Antlers-Arundel, had non-significant p-values of 0.76 and 0.32, respectively. This data indicates the Cloverly and Antlers faunas are morphologically significantly different, at a minimum in tooth morphology. It’s possible the two non-significant pairs, both in comparison to the Arundel, are suffering from the Arundel’s small sample size, but additional data is needed for further assessment.

Morphological data coupled with geochronologic data from the host deposits informs a hypothesis of Deinonychus dispersal across the continent. Recent studies have found the Arundel to encompass the Aptian stage, specifically a carbon isotope excursion associated with OAE 1a, which has been dated to ~118Ma; geochronologic studies of the fossiliferous horizons of the Cloverly have dated U-Pb of zircons to ~113-107Ma and the Antlers to ~113-106Ma. When these dates are coupled with morphologic data, it can be inferred the taxon originated in Maryland, based on known occurrences, and dispersed westward, evolving the two morphologically distinct Cloverly and Antlers populations. Further study is needed to verify this hypothesis, but this study exemplifies the power of morphometrics on isolated teeth and the information that can be obtained when data from other sources are used in tandem.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10940

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