[dinosaur] Abelisaurid theropod parallel tracks from Argentina show gregarious behavior

Ben Creisler
[email protected]

A new paper:

Arturo Miguel Heredia, Ignacio Díaz-Martínez, Pablo José Pazos, Marcos
Comerio & Diana Elizabeth Fernández (2019)
Gregarious behaviour among non-avian theropods inferred from trackways: A
case study from the Cretaceous (Cenomanian) Candeleros Formation of
Patagonia, Argentina
Palaeogeography, Palaeoclimatology, Palaeoecology, Article 109480 (advance
online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.palaeo.2019.109480&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=hdbxtJmP9hzdVvEeDbVIqnLzIFnQBLbaTB4Kf2p3ImA&s=C62hYhzwKLe6kHtHdT_CEnivJJUY1LTpzDbmyRAt0sU&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_abs_pii_S0031018219306959&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=hdbxtJmP9hzdVvEeDbVIqnLzIFnQBLbaTB4Kf2p3ImA&s=2oD8z-bEUDGshI1PACpF5XAcHOczpEAFXoDVTv46PXA&e= 

Highlights

Parallel theropod trackways from the Cretaceous (Cenomanian) of Patagonia
are described.
Abelisaurid theropods are suggested as trackmakers and gregarious behaviour
is inferred.
Tracks are preserved as shallow undertracks in floodplain deposits.
Swelling clays and microbial mats may have played a role in track
preservation.

Abstract

Gregarious behaviour among dinosaurs has been inferred from several lines
of evidence (monospecific bonebeds, skeletal morphology, phylogenetic
inferences, comparison with modern ecosystems and parallel trackways with
particular characteristics), but is relatively poorly documented for
non-avian theropods. Here, we report five parallel theropod trackways of
large track size (average length of 28 cm) in the Cretaceous (Cenomanian)
Candeleros Formation from northwestern Patagonia, Argentina. The tracks are
provisionally assigned to aff. Asianopodus pulvinicalx and considering the
autopod morphology of the theropod taxa documented in the Candeleros
Formation, abelisaurid theropods are suggested as trackmakers. The
trackways possess similar stride, speed estimation, direction and
preservational features, and track show uniform depth and do not overlap.
Physical barriers (i.e., large fluvial channels or perennial lake) that
could influence the direction of the theropod trackmaker gaits were not
recognized in the section. Taking into account these considerations, a
gregarious behaviour for the abelisaurid theropod trackmakers is proposed.
The tracks are preserved as shallow undertracks in a medium-grained
sandstone bed deposited in a floodplain setting. The tracking surface is
interpreted as the overlaying layer of muddy-siltstone. The occurrence of
swelling clays and microbial mats in the track-bearing level could have
contributed to the substrate stabilization and their role in the
preservation is discussed.