The bird-like tridactyl (three-toed) footprints found at the site of Maphutseng in Lesotho predate the oldest known bird body fossils by approximately 60 million years, and were left by an unknown animal, likely an early dinosaur.
Photographs, interpretive outlines and false-color depth maps of distinct traces associated with Trisauropodiscus at Maphutseng, Lesotho: (A) markings resembling either pecking and probing activity, partial track (digit) impressions or invertebrate traces; (B) markings resembling either a continuous pecking trace or invertebrate trace; (C) unequivocal invertebrate trace and markings resembling either pecking and probing activities, or partial track (digit) impressions or invertebrate traces. Image credit: M. Abrahams & E.M. Bordy, doi: 10.1371/journal.pone.0293021.
“Birds are one of the most diverse groups of animals on Earth with around 10,000 living species, yet their early evolutionary history is still shrouded in mystery,” said University of Cape Town paleontologists Miengah Abrahams and Emese Bordy.
“The dinosaurian origin of modern birds unequivocally points to Maniraptora, a group of theropod dinosaurs, but the timing of the origin of birds is contested.”
“The oldest body fossil record of early birds comprises Middle to Late Jurassic (150-160 million years ago) Aurornis, Anchiornis, Archaeopteryx and Xiaotingia, while dinosaurian footprints with bird-like morphologies are known since the Late Triassic.”
“The early birds known from body fossils likely originated in the Early or pre-Jurassic, although, to-date, this is unconfirmed by the early osteological record that is exceedingly fragmentary.”
“The only Late Triassic body fossil specimen posited to be bird-like is Protoavis, but this assessment is based on ambiguous material and is not widely accepted to be a basal bird.”
“In this context, all ancient bird-like paleontological discoveries are vital for unravelling both the origin of birds and the evolution of dinosaurs.”
In the new study, the researchers reassessed the fossilized footprints — previously assigned to the ichnogenus Trisauropodiscus — from four locations in Lesotho, southern Africa.
They also provided a detailed field-based description of footprints from an 80-m-long tracksite at the site of Maphutseng.
“Multiple tridactyl tracks with a ‘proto-avian’ morphology from the Late Triassic and Early Jurassic of southern Africa were assigned to Trisauropodiscus in the mid-1900s,” they explained.
“Based on the interpretive sketches and brief descriptions, the avian affinity of Trisauropodiscus has been hotly debated: some authors have likened the tracks to Anomoepus, accepted to be attributed to an ornithischian dinosaur, while others have agreed with its bird-like morphology, likening it to Gruipeda, which is attributed to plover-like birds.”
Their findings suggest that there are two distinct Trisauropodiscus morphotypes, one of which resembles footprints made by birds and the second is similar to certain non-avian dinosaur tracks.
The most ancient of these footprints are over 210 million years old — approximately 60 million years older than the earliest known body fossils of true birds.
It’s possible that these tracks were produced by early dinosaurs, and potentially even early members of a near-bird lineage, but there could also have been other reptiles that convergently evolved bird-like feet.
“Whoever the trackmakers are, these footprints establish the origin of bird-like feet at least as early as the Late Triassic epoch,” the paleontologists said.
The results appear online in the journal PLoS ONE.
M. Abrahams & E.M. Bordy. 2023. The oldest fossil bird-like footprints from the upper Triassic of southern Africa. PLoS ONE 18 (11): e0293021; doi: 10.1371/journal.pone.0293021
Source : Breaking Science News