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Tenuicruris piscanexum becomes the second Cretaceous bird named from Australia
Two bird bones found near Richmond, Queensland, belong to Tenuicruris piscanexum, only the second Cretaceous bird formally named from Australia. In a record of fewer than a dozen bones, a second named species gives each new find something to be measured against.
The Scientist · Science desk
What happened
- Kevin Petersen, a former Kronosaurus Korner curator, found the first bone in Richmond's public collecting areas, in a 'fish mash layer' packed with fish remains and marine reptile teeth.
- A week later, after rain, he found a second bone on a rock slab and sent photographs of both to Matt White at the University of New England.
- White identified the pair as a tibiotarsus and a tarsometatarsus, the fused foot bones of a bird.
- A phylogenetic assessment places both specimens in Enantiornithes, the dominant and diverse group of Mesozoic birds worldwide.
- The genus name Tenuicruris means 'slender leg', for the gracile limbs, and piscanexum ties the species to the fish-rich layer that held it.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Both named Australian Cretaceous birds rest on isolated hindlimb bones, so anything said about their biology beyond limb shape has to wait for more complete skeletons.
- capability Because the bones were scanned inside their concretion, they remain intact for re-study or later preparation if more Toolebuc bird material turns up.
- precedent A named species from Richmond's public collecting areas shows that finds made there can reach the formal record when photographed and passed to a specialist, as Petersen's were.
The oldest bird remains in Australia's Cretaceous record come from Early Cretaceous deposits in Victoria, about 128 million to 120 million years old, and scattered feathers and footprints hint at more diversity than the bones show [14]. Lightning Ridge has added opalized bird material from the Griman Creek Formation, about 110 million to 97 million years old [15]. The Victorian remains are roughly 15 to 23 million years older than the Richmond bones [1].
Both new bones were well preserved but partly encased in concretion, and the team chose not to fully excavate them [8]. Joseph Bevitt scanned them at the Australian Nuclear Science and Technology Organisation, and White converted the scan data into 3D meshes that show the bones inside the rock [9]. That choice mattered for the comparison. Nanantius eos, the only other named Cretaceous bird from Australia, was described in 1986 from an isolated tibiotarsus [16]. The nondestructive scans let the team compare the new tibiotarsus with it directly, and they revealed clear anatomical differences [10].
"I recognized them immediately as bird bones," White said. "These specimens are especially significant because so few have been found in Australia, and none were directly comparable until now." [6]
The phys.org report, which summarises a paper in the Journal of Vertebrate Paleontology [3], does not explain how the two bones, found at separate sites, were assigned to one species [1]. Placement in Enantiornithes [12] says which large group the bird belongs to. The species-level evidence the report describes is the tibiotarsus comparison with Nanantius [10].
Dean Lomax of the University of Bristol examined the specimens during Queensland's Dinosaur Week. "Although the newly discovered remains represent isolated bones, they are exceptionally rare," he said [18].
The bones come from the Toolebuc Formation, about 105 million years old, a unit that already yields pliosaurs, plesiosaurs, turtles, sharks, chimaeroids, bony fish and pterosaurs [13]. Nanantius comes from the same formation, and one of the few other Nanantius tibiotarsi reported was preserved with ichthyosaur gut contents [16].
I think the naming is a careful use of scarce material, with one condition attached. A species separated on the shape of one bone type depends on how much that bone varies within a species, and here the variation is thinly sampled. Only a few Nanantius tibiotarsi have been reported [16], and Tenuicruris has a single tibiotarsus to set against them [7].
What to watch
- Further tibiotarsi from the Toolebuc Formation that can be assigned to Tenuicruris or Nanantius, which would test whether the scanned anatomical differences hold across individuals.
- Any associated or articulated bird skeleton from the Richmond fish mash layer, which could show whether a tibiotarsus and tarsometatarsus like these belong to one animal.