T237 New Insights on Arthropod Paleobiology

Wednesday, 13 October 2021
1:30 PM - 5:30 PM
E141/E142 (Hybrid Room)

CRETACEOUS POLAR ARTHROPODS ON WALKABOUTS: NEWLY DISCOVERED ARTHROPOD TRACE FOSSILS FROM THE WONTHAGGI FORMATION (BARREMIAN), VICTORIA, AUSTRALIA

Paper number: T237-16
Program: Technical Sessions
Time: 5:00 PM – 5:15 PM

Authors

Abstract

Lower Cretaceous (Valangian to Albian, ~132-105 mya) rocks of Victoria, Australia are well known for their fossils from circumpolar alluvial, fluvial, and lacustrine environments. Body fossils represent communities with moderate biodiversity, including: vascular plants (ferns, lycophytes, conifers, angiosperms); bivalves; arthropods (insects, arachnids, limulids, crayfish); fishes (actinopterygians, dipnoans); temnospondyls; chelonians; plesiosaurs; crocodylomorphs; and non-avian and avian dinosaurs. Since 2006, increased recognition of trace fossils in these strata – such as crayfish burrows, dinosaur tracks, and bird tracks – have added further insights about organismal interactions with polar environments. However, trace fossil assemblages lacked arthropod trackways, which would help better understand arthropod behaviors in the context of Cretaceous polar environments.

Thus we are pleased to report the discovery of multiple arthropod trackways in fine-grained fluvial-floodplain sandstones from the Wonthaggi Formation (Barremian) near Inverloch, Victoria. Two distinctive types of trackways are evident, with track series and sets that allow for preliminary classification of their tracemakers. Type 1 is represented by 16-18 mm wide and straight to meandering trackways, each with 3 tracks/series and 6 tracks/set; trackway lengths vary from 12-49 cm long (n=7). Type 2 trackway consists of a single specimen, ~5 cm wide and 30 cm long, with at least 3 tracks/series and parallel linear impressions within the trackway. We propose the Type 1 trackways were made by insects, whereas the Type 2 trackway may have been from a crayfish. These arthropod trackways are the first reported from the Cretaceous of Victoria, and among the few from Cretaceous polar environments. Such trackways also likely represent seasonal behaviors, with insects and crayfish walking on emergent surfaces after overwintering, spring thaws, and flooding. These trace fossils thus help give tantalizing insights on arthropod adaptations to these extreme environments during the Cretaceous.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-364259

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