Paleontology is an ever-changing field, as are all other areas of science. thepaintpaddock was conceived upon that notion. As technology and our wealth of knowledge increases, we’ll do away with outdated ideas.
Such is the case – twice, even – with Brontosaurus.
Discovered and named by Othinel Charles Marsh in 1879, Brontosaurus is one of the many dinosaurs uncovered during the “fossil wars” of the late nineteenth century (I’ll be sure to write up on that sometime soon, it’s interesting stuff). A number of the genera named and described during this period of time have since been either synonymized (as in “this animal and this other animal are actually the same thing”) or are remaining in limbo. Sometimes the material is too fragmentary to even confidently call it a dinosaur!
Dinosaurs were still very poorly understood in the time of Marsh and his peers. Though it was clear that these were hulking reptiles that have long since expired, there wasn’t much prior material to go on. In the name of good spirits, it was “make do with what you’ve got.” What Marsh had was a partial skeleton that lacked a skull, which was and still is the tell-all for paleontologists in distinguishing genera.
Deeming the animal too similar to a contemporary sauropod – Apatosaurus – the lack of available material led to the synonymization of the two genera. Brontosaurus excelsus and other Brontosaurus species were re-labelled as Apatosaurus excelsus and so on. What happened in the ensuing decades was a pure cluster%^&. “Apatosaurus excelsus” (and only excelsus) still didn’t have a skull. Material eventually found to have belonged to Brachiosaurus and Camarasaurus were tried and failed to be assigned to this headache of an animal.
Light contentions from paleontologists were scattered about the remainder of the twentieth century in regards to the validity of Apatosaurus excelsus, though the consensus remained that Brontosaurus was never a separate genus…until 2015.
An extensive study of the entire sauropod family was conducted by Tschopp et al. last year, which found that the skeletal remains between the type species of Apatosaurus (sp. ajax) and A. excelsus to be too divergent to be from the same genus. In taxonomy and biology, a type species describes the “baseline” for the genus. Think of it as the anatomical qualifications to be that genus. A. excelsus had too many bones that did not match with A. ajax in terms of traits such as proportion, creating a reclassification of A. excelsus to…
Funny how that works, isn’t it?
Brontosaurus‘s fall and rise relied on the keen eye of scientists from the era of the Bone Wars and the twenty-first century. Both conclusions were made using the available material and observation techniques. That’s why, in science, being “right” is typically only a temporary victory.
- Brontosaurus is discovered in the late-1800s.
- There isn’t a skull. Back then, skulls were the primary (and are still the easiest) way to distinguish between dinosaurs. Scientists consider the skeletons between Brontosaurus and Apatosaurus are too similar to be separate, and synonymize all Brontosaurus species as Apatosaurus.
- Fast-forward to 2015.
- We know enough about dinosaurs to notice fine differences in bone structure. The bones between A. ajax (the type species) and A. excelsus are too different to be from the same genus.
- A. excelsus is re-separated as Brontosaurus.
Until next time!
Note: Brontosaurus excelsus still doesn’t have a skull. We guess it looked pretty similar to Apatosaurus‘s, though. Yay for our MVP – phylogenetic bracketing!