Better Know a [Aussie] – The Rainbow Serpent of Oz


L. Frank Baum might roll in his grave if I alluded to gay dinosaurs in Oz. Well, insofar as dinosaurs with rainbow-colored bones from Oz (aka, Australia) might be considered “gay.” But that’s just what Kakuru kujani is … a dinosaur based on a tibia that’s been opalized,  transformed into a rainbow-colored mineral, and it’s from Australia. It also just so happens that various indigenous peoples from Australia have legends of a living rainbow, a serpent from Dreamtime, and one of its names (from the Guyani of southern Australia) is “Kakuru.”

History

Kakuru kujani was named from a nearly complete tibia, particula fibula, and complete intermediate pedal phalanx (of unknown position) [1]. I had previously treated Kakuru kujani here, but feel the need to treat this taxon here. This is due in large part to two recent papers that have examined the material in order to qualify the material referred to the taxon. This appears to be no mean feat: as noted above, the material has been transformed into opal, a semi-precious gem, and unlike standard fossils, this makes fragments of bone collectible as souvenirs that can be transformed into gems that no longer resemble their original material. Mined from various placed, opalized bones have been recovered as bits and pieces, surface float, and (rarely) whole bones and (most rarest of all) whole skeletons. As the market to buy and render the material is high when present, the preservation of material is important, so we are quite lucky we continue to possess this material.

Tibia (SAM P17926) of Kakuru kujani in A, anterior view; B, posterior view; C, anteromedial view; and D, posterolateral view. Scale bar equals 4.5cm in A and 1 cm in B-D. Used with permission of the owner; courtesy Dann Pigdon.

Kakuru kujani as we know it is fairly detailed [1]. SAM P17926 is a unique form of type, a plastoholotype, developed when the original holotype is unavailable, or the holotype is simply made from a cast of the original. The original tibia is currently in private hands, but with special attention, has been examined by a few people, and their observations supplement that of the original cast and new casts taken of the original material. When originally examined, the material was owned by a private collector who made it available for study and casting. Shortly thereafter, the owner withdrew the material from the public, and it has largely remained this way until the last ten years, when it has been increasingly more available. Between then and when originally described, only a cast and initial description existed.

Kakuru kujani represents one of the first well-represented theropod dinosaurs from Australia, based on material more substantial than tracks or claws or teeth. Ornithischians and sauropods have been known in better detail, but theropods are rare. For this reason, Kakuru kujani has played a somewhat exaggerated role in paleontological perspectives on Australia’s Cretaceous (or even Mesozoic) record. As such, it tends to take a pivotal and often anachronistic role. Despite this, much of what we know is based on very, very little, and what there is of it is not in that good of shape [2,3].

Quality of the Material

Distal tibia (SAM P17926) of Kakuru kujani. A, distal end in anterior view, as preserved; B, distal end in distal view; C, distal end as preserved in life, showing placement of an intact fibula, astragalus, and probably position of the calcaneum. The shape of the astragalar condyles is hypothetical. aap, ascending process of the astragalus; asc, astragalar corpus; c, calcaneum; cf, cranial fossa for the astragalus; cr, cranial ridge; fi, fibula; ff, facet for the fibula; mm, medial malleolus; t, tibia.

SAM P17926 is a tibia with two small pieces of fibula attached (see first figure above). The material represents about 90% or more of the length of the entire bone, missing only the proximal end included the femoral cotyles, and the cnemial crest; it also is missing one or more small sections of the shaft, and thus obscures the true length of the bone. The distal end is exceptionally well-preserved compared to the rest of the shaft, although it is in hardly perfect condition, showing weathering and cracks [2,3] that have allowed some authors (e.g., [1]) to treat the material as uniquely representative of a small group of theropod dinosaurs. One group to which Kakuru kujani has been refered was Oviraptorosauria, which is one of the reasons I am treating this taxon here.

The most recent detailed examination comes from two new papers ([2,3]) which have examined not only the original but also new casts of the tibia and associated fossils. These works show that the tibia is very much cracked, weathered, and lacking in the details originally ascribed to it, most notably two of the most distinctive and apomorphic qualities: the vertical ridge with corresponding sulcus within the facet for the astragalar ascending process, and the derived shape of the medial malleolus of the distal end. Both appear to be artefacts of preservation, rather than evolution, and they render some details of the tibia problematic for analysis [2,3].

Kakuru a nomen dubium?

Both [2] and [3] used the lack of derived features, once they’d rendered these apomorphies to artefacts, to preclude that Kakuru kujani is a nomen dubium. This designation, as I’ve argued before, is typically used for a variety of situations, and in this case, it is done because the material appears to lack features that designate it more securely than Theropoda. One may argue then, that without more secure details, it is difficult to assert the taxon is even unique enough to deserve a name; it is also possible to argue that there are some features of the tibia that are distinct from other taxa, enough to provide Kakuru kujani with some apomorphic suites which allow it to be readily identified one the basis of the tibia, and this is almost certainly true. The question of whether the ability to derive an identification on the basis of a set of features, none unique on their own, is worthy of designating taxonomy is another matter, and one I can hardly hope to resolve so easily or by myself. I should like to note that being unable to place Kakuru kujaniwithin a particular taxon is irrelevant if one considered supraspecific or suprageneric taxa identical; in general, Theropoda is as worthy and valid a container as Oviraptoridae, and in this case, one need not be so broad or strict in the degree of inclusiveness of the taxon to which a particular other taxon is being referred. It is also problematiuc to assume that all genera should be contained within a family-rank taxon; while the ICZN does assert this, forcing many systematists who could not easily place their taxon to a given group to nominate monoitypic families (and higher rank taxa) to include their singular genera (and often singular species!), this has fallen to the wayside in some branches of vertebrate paleontology.

As I noted in my previous essay on Kakuru kujani, an explicit comparison with other dinosaurian tibiae, as well as slender crocodylian tibiae, allows us to consider some features of the holotype. Following this, we should be able to see whether these features are comparable enough to warrant taxonomy. But I won’t go through that too much today: This is merely a review rather than a systematic analysis. One thing is clear, however: Kakuru kujani has failed to be placed in virtually all recent systematic analyses testing through the cladistic treatment. Is it possible to place what we know of Kakuru based on the holotype? That would depend on the refinement of the analysis and its ability to distinguish character traits discretely enough to be informative of the holotype.

[1] Molnar, R. E. & Pledge, N. S. 1980. A new theropod dinosaur from South Australia. Alcheringa 4:281-287.
[2] Agnolin, F. L., Ezcurra, M. D., Pais, D. F. & Salisbury, S. W. 2010. A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities. Journal of Systematic Palaeontology 8(2):257-300.
[3] Barrett, P. M., Kear, B. P. & Benson, R. B. J. 2010. Opalised archosaur remains from the Lower Cretaceous of South Australia. Alcheringa 34, 293-301.

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2 Responses to Better Know a [Aussie] – The Rainbow Serpent of Oz

  1. mattvr says:

    Thanks for doing this analysis.
    So much Australian material is fragmentary and, at least to lay people, left un-reviewed for decades at a time.

  2. Andrea Cau says:

    Based on the combination of characters described by Barrett et al. (2010), “Kakuru” should be considered a basal coelurosaur (the authors considers it a tetanuran of uncertain affinities, but I think a more inclusive placement is possible, based at least on the tall facet for the astragalar ascending process shared by most coelurosaurs. The reduced medial extention of the astragalar facet excludes it from Maniraptoriformes and derived Tyrannosauroidea, so it may be a basal coelurosaur).

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