This week, the internet’s latched onto Torvosaurus and not let go. However, there’s been plenty more new palaeontological discoveries than a new European megacarnivore.
Torvosaurus gurneyi: Europe’s new heavyweight
If you haven’t heard about the new species of Torvosaurus that’s been discovered this week, then you’ve either been hiding under a rock, or you just simply hate dinosaurs. The news come from Portugal, after Hendrickx & Mateus redescribed bones initially thought to belong to the American species Torvosaurus tanneri. They name a new species, Torvosaurus gurneyi (named after James Gurney, artist of the wonderful Dinotopia series), distinct from T. tanneri based on numerous features including less teeth on the maxilla (for example). Dated to 157-145 Ma, T. gurneyi roamed the late Jurassic, and it would be hard to miss, considering size estimates settle around 33ft in length. Sure, it’s not T. rex, Spinosaurus or Giganotosaurus, but it does mean that T. gurneyi is the largest carniverous dinosaur discovered in Europe to date. So what does this all mean? Considering two species are now found on either side of the Atlantic, Hendrickx & Mateus hypothesise that some form of geographical barrier (such as geological uplift) separated multiple populations of Torvosaurus, and these (now completely separate) populations evolved to different local conditions (this idea is commonly termed vicariance).
Adipose fins no longer (of a) single (origin).
Far from it for me to encroach on Richard’s beloved fish, but this week new insight into adipose fins has shed some light on convergent evolution of fins (and vertebrate limbs more generally). You’re wondering what an adipose fin is, aren’t you? Go and look at the figure below.
Moving on, Stewart et al., using phylogenetic and anatomical evidence from over 600 species of fish concluded that the adipose fin, despite being widely regarded as vestigial with no clear/agreeable function, has been found to have evolved repeatedly and independently. Adipose fins have also evolved multiple features such as fin rays, which suggests that complexity and new types of tissue can evolve by activating certain developmental modules. Stewart et al. earmark this study as important to future work on the evolution of the limbs (and their complexity) in vertebrates. The study also challenges the long held notion that dermal skeleton evolved first, followed by the evolution of the endoskeleton. It also hints thats one may evolve without the other.
Daohugou, Jehol’s attractive older sibling
Yes, that was an unnecessarily creepy title. Moving on. The Jehol Biota, over in China is a lower Cretaceous ecosystem, represented by numerous localities (mainly of the exceptionally preserved lagerstatte variety). Jehol localities have given us a plethora of exceptionally preserved dinosaurs, pterosaurs, birds and mammals over the last 20 ish years. Recently, older deposits (Jurassic) from the same geographical region have been discovered. Sullivan et al. link the Daohugou locality to numerous other localities by the presence of a salamander, Chunerpeton tianyiensis, the key species that confirms the link of these localities to form the Daohugou biota. Much like in last week’s What’s New(s), with the discovery of a ‘new Burgess Shale’, this exceptionally preserved ecosystem has an incredible potential to provide vital information on the evolution of dinosaurs, birds, pterosaurs and mammals. The locality has already produced 13 well preserved pterosaurs (as well as ﬁve salamanders, two lizards, ﬁve dinosaurs, four mammals, oh, and a frog), so the future looks bright for Jehol’s older sibling.
Ocepeia: a very old afrotherian
The final two stories revolve around Cenozoic taxa, because it’s all too apparent that TDS is considerably lacking in Cenozoic palaeontological goodness. The first story centres around afrotherians, a superorder of mammals that have an African origin (including elephants, tenrecs, aardvarks, hyraxes and dugongs). The afrotherian in question is Ocepeia (O. grandis and O. daouiensis). A Ocepeia skull was discovered in the Selandian of Ouled Abdoun Basin (what a name) in Morocco. It dates to around 61 Ma, which immediately makes it the oldest afrotherian skull to ever be discovered. Now this is interesting, because this skull shows a mixture of primitive and derived features, as well as a mix of ungulate-like afrotherian (elephants, sea cows and hyraxes) and insectivore-like afrotherian (aardvarks, sengis, tenrecs and golden moles) features. This means that Ocepeia appears to be a ‘transitional form’ between these two subgroups of Afrotheria. This in turn provides significant evidence that Afrotheria may well have evolved specifically within Africa in the latest Cretaceous/early Tertiary. Pretty cool, for a mammal.
Gastornis goes vegetarian for lent
Second in our short series of Cenozoic news is Gastornis. If you haven’t heard, Gastornis is a 2m tall terror bird which lived approximately 56-45 Ma (Paleocene-Eocene kinda time), that was previously thought to terrorise and eat small horse ancestors. This horse-heavy carniverous diet has been but into question for some time, and new evidence from Angst et al. suggests that whilst looking terrifying, only the plants of the Paleocene and Eocene had to worry about that enormous beak. Angst et al. form two lines of evidence, first they looked at carbon isotopes of bone apatite, and compared it to other herbivores (both mammals and birds). They found the results of this isotope analysis to be similar to the results gained from the other herbiverous taxa. Secondly, they look at (hypothetical) reconstructed jaw muscles of Gastornis, and again found that it shared similar looking jaw muscles to other herbiverous birds. Don’t worry Gastornis, you’re still scary to me (I mean your an almost 7 foot tall bird with a beak that looks like it can cut a man in half).
Hendrickx C., Mateus O. (2014) Torvosaurus gurneyi n. sp., the Largest Terrestrial Predator from Europe, and a Proposed Terminology of the Maxilla Anatomy in Nonavian Theropods. PLoS ONE 9(3): e88905. doi:10.1371/journal.pone.0088905
Stewart, T. A. et al. (2014). The origins of adipose fins: an analysis of homoplasy and the serial homology of vertebrate appendages.Proceedings of the Royal Society B: Biological Sciences, 2014; 281 (1781): 20133120 DOI: 10.1098/rspb.2013.3120
Sullivan, C. et al. (2014). The vertebrates of the Jurassic Daohugou Biota of northeastern China. Journal of Vertebrate Paleontology 34 (2): 243 DOI:10.1080/02724634.2013.787316
Gheerbrant E. et al. (2014) Ocepeia (Middle Paleocene of Morocco): The Oldest Skull of an Afrotherian Mammal. PLoS ONE 9(2): e89739. doi:10.1371/journal.pone.0089739
Angst, D. et al. (2014). Isotopic and anatomical evidence of a herbiverous in the Early Tertiary giant bird Gastornis. Implications for the structure of Paleocene terrestrial ecosystems. Naturwissenschaften DOI 10.1007/s00114-014-1158-2