Tuesday, August 26, 2014

Another claimed "feathered dinosaur"

Let's begin with an accumulation of material about Kulindadromeus:

Kulindadromeus is a feathered, herbivorous dinosaur, a basal neornithischian from the Jurassic of Russia. Its integument is evidence for the trait being basal to Dinosauria as a whole, rather than just to Coelurosauria, as previously suspected.
Kulindadromeus is significant in that the various specimens show large parts of its integument. This includes imbricated rows of scales on top of its tail and also a covering of scales branching into feather-like structures, which until its discovery were thought to be exclusive to the Theropoda, of the saurischian-line.[5] The feather remains discovered are of three types, adding a level of complexity to the evolution of feathers in dinosaurs.[4] The first type consists of hair-like filaments covering the trunk, neck and head. These are up to three centimetres long and resemble the stage 1 "dino-fuzz" already known from theropods like Sinosauropteryx. The second type is represented by groups of six or seven downwards projecting up to 1.5 centimetres long filaments, together originating from a base plate. These are present on the upper arm and thigh. They resemble the type 3 feathers of theropods. The base plates are ordered in a hexagonal pattern but do not touch each other. The third type is unique. It was found on the upper lower legs and consists of bundles of six or seven ribbon-like structures, up to two centimetres long. Each ribbon is constructed from about ten parallel filaments up to 0.1 millimetres wide.[1]
Godefroit et al. concluded that the filaments earlier reported in Ornithischia, with Psittacosaurus and Tianyulong, could be homologous to the "protofeathers" found in non-avian theropods. With known feather-like structures in pterosaurs, there is evidence for it being basal to Ornithodira.

A Jurassic ornithischian dinosaur from Siberia with both feathers and scales
  • Paul Spagna1
    Middle Jurassic to Early Cretaceous deposits from northeastern China have yielded varied theropod dinosaurs bearing feathers. Filamentous integumentary structures have also been described in ornithischian dinosaurs, but whether these filaments can be regarded as part of the evolutionary lineage toward feathers remains controversial. Here we describe a new basal neornithischian dinosaur from the Jurassic of Siberia with small scales around the distal hindlimb, larger imbricated scales around the tail, monofilaments around the head and the thorax, and more complex featherlike structures around the humerus, the femur, and the tibia. The discovery of these branched integumentary structures outside theropods suggests that featherlike structures coexisted with scales and were potentially widespread among the entire dinosaur clade; feathers may thus have been present in the earliest dinosaurs.
    The scales on Kulindadromeus resemble the scaly skin seen on some birds, the study says, which also argues for a deep genetic root linking dinosaurs to birds.
    Two earlier ornithischian dinosaur discoveries, both from China, had hinted that featherlike bristles had covered dinosaurs, notes paleontologist Stephen Brusatte of the United Kingdom's University of Edinburgh.
    "But the new Siberian fossils are the best example yet that some ornithischian [beaked] dinosaurs had feathers, so it wasn't only the theropods that had downy coats," Brusatte says.
    "This does mean that we can now be very confident that feathers weren't just an invention of birds and their closest relatives, but evolved much deeper in dinosaur history," he adds. "I think that the common ancestor of dinosaurs probably had feathers, and that all dinosaurs had some type of feather, just like all mammals have some type of hair."










    For reference:
    Stage 1:

    From the supplementary material:
    We considered attempting to describe the feather morphotypes in Kulindadromeus using the nomenclature of Prum et al. (52, 53) or of Xu et al. (21, 22). However, except for our monofilaments (which correspond well to Type 1 in Xu et al.), we could not assign with confidence the other two feather morphotypes in Kulindadromeus to categories described by Prum et al. or Xu et al. Further, fundamental discrepancies between these two previously published nomenclature systems remain to be resolved. Thus we felt that until new fossil material and a synthesis of existing nomenclature systems are available, interpretations of direct homologies between complex feather-types in Kulindadromeus and in Prum et al. or Xu et al. would be premature.

    The fact that feathers appear to be growing out of scale-like features suggests, as biologists have long assumed, that feathers actually evolved from scales, though the authors suggest that the “scales” on birds’ legs and feet are not persistent scales derived from their reptilian ancestors, but evolved back from feathers! Since scales certainly preceded feathers in the fossil record, this shows that truly new structures, certainly involving new genetic information, can evolve (and then be lost, reverting on birds’ feet to scales). That belies the common creationist criticism that new genetic information can’t evolve (we saw that from one commenter earlier today).
    But Dr Paul Barrett of the Natural History Museum in London, has doubts.
    "Most feathers have a branching structure," he told BBC News.
    "Instead these look like little streamers coming from a central plate. No bird has that structure in any part of its plumage and none of the developmental models that biologists use to understand the evolution of feathers includes a stage that has anything like that kind of anatomy."
    Kulindadromeus adds a whole new dimension to understanding feather evolution, Vinther says, pointing to the fact that the three feather types found as imprints with the fossils are different from ones found on feathered dinosaurs or modern birds.
    What exactly did all these different feathers do? "I don't know; nobody knows for sure," Godefroit says. "These animals couldn't fly, that's all we can tell you."
    So I find it quite strange and disheartening that Godefroit et al.—despite being fairly objective in their supplementary material—go completely gung-ho in calling these structures feathers.

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