As stated from the beginning
of this blog, I am more interested in clade origins and relationships than any other paleo topic (like diet or asteroid impact). So the following review of recent and important dino books will focus on what they say about the origin of dinos: i.e. what happens when taxon exclusion meets the LRT.
Dinosaurs: a concise natural history (Weishampel and Fastovsky 2009)
This book defines the living reptiles as: turtles + diapsids (including living birds)
That is outdated
according to the large reptile tree (LRT, 1240 taxa) where mammals are also reptiles, and diapsids are not monophyletic. According to the LRT reptiles can be defined as any archosauromorph (e.g. Eldeceeon, mammals, ichthyosaurs, archosaurs), plus any lepidosauromorph (e.g. Urumqia, captorhinids, turtles, lepidosaurs), their last common ancestor (e.g. the amphibian-like reptiles Silvanerpeton, Gephyrostegus) and all descendants.
In the W+F book there are two main clades of Diapsids: Lepidosauromorpha and Archosauromorpha.
This is outdated.
In the W+F book there are five main clades of Archosauromorpha: Rhynchosauria, Prolacertiformes, Crurotarsi (including Crocodylia), Pterosauria, Dinosauria.
This is outdated.
Their way-too-simplified-cladogram is what makes paleontology and evolution look bad due to taxon exclusion. No taxa display a gradual accumulation of traits in the W+F cladogram. You can’t have super specialized rhynchosaurs at the base of any large clade. They are terminal taxa arising from sphenodontids in the LRT. Pterosaurs share nothing in common with their purported W+F sisters, crocs and dinos. Pterosaurs actually arise from fenestrasaur, tritosaur lepidosaurs. Another terminal taxon, Tanystropheus, the poster-child for prolacertiforms is not related to Prolacerta in the LRT, but arises from Huehuecuetzpalli, Macrocnemus and Langobardisaurus, among others, not far from pterosaurs. Derived taxa in this clade share a nearly identical foot morphology.
The W+F book presents two hypotheses of dinosaur origins:
- pterosaurs + Lagosuchus + dinosaurs (Gauthier and Padian) = Ornithodira.
- Lagosuchus, Lagerpeton, Pseudolagoschus, Marasuchus (Sereno) = dinosaur precursors. Pterosaurs are more distantly related.
These two hypotheses are both outdated
Pterosaurs are lepidosaurs, unrelated to dinosaurs. Lagerpeton is a sister to the chanaresuchid, Tropidosuchus. Marasuchus is a theropod, not a dinosaur outgroup. In the LRT bipedal crocs are the proximal outgroups to dinosaurs.
The rise and fall of the Dinosaurs. Brusatte 2018. Don’t confuse this 2018 book with ‘The rise and fall of the dinosaur’ (singular, not plural) by Wallace 1987.
Brusatte clings to his wrong-from-the-start hypothesis (Brusatte et al. 2011) that the first dinosaurs are represented by Prorotodactylus (Fig. 3) footprints in the Early Triassic (251 mya). Prorotodactylus tracks were actually made by tritosaur lepidosaurs, like Macrocnemus, with a small, symmetrical, 5-fingered manus and an asymmetric pes with a short digit 5.
Brusatte’s mistake comes from a misunderstanding of reptile relationships, probably because he was schooled using the Weishampel and Fastovsky books (see above). Brusatte was familiar with the invalid Lagerpeton hypothesis of dinosaur origins because he was an undergrad student of Paul Sereno (see above). Thus Brusatte was ready to accept the asymmetric pedal track of Prorotodactylus track as homologous with that of Lagerpeton. Brusatte was also a student of Mike Benton. You might remember, Benton infamously promoted the bipedal croc with tiny hands and no pedal digit 5, Scleromochlus, as a pterosaur sister. Later Benton joined with his other student, David Hone (Hone and Benton 2007, 2008) in deciding to include, then exclude Peters 2000 data on fenestrasaurs. In so doing Hone gained his PhD and pterosaur origins were taken back to the dark ages. We talked about professor/student influences earlier here. In my youth I was influenced by books and professors, so I know how readily that can happen. If the influence is valid, that’s fine. If not, that’s a problem.
The actual last common ancestor of all dinos (and all crocs, too) in the LRT is the Túcuman specimen wrongly attributed to Gracilisuchus, PVL 4597 (Lecuona and Desojo 2011; Fig. 4) which has been known for 7 years.
It’s unfortunately ironic
that as much as Dr. Brusatte loves tyrannosaurs, as co-author (Lü and Brusatte 2015) he also misidentified Zhenyuanlong as a dromaeosaurid, not a tyrannosaur ancestor, as we looked at earlier here. He also listed a number of unrelated taxa, like Dilong, as tyrannosaur ancestors in an earlier magazine article discussed here. So his track record regarding dino systematics is not validated in the LRT.
let’s remember that paleontology works at a snail’s pace. We’ve know that birds are dinosaurs since TH Huxley looked at Archaeopteryx in the 1860s, but workers were not keen to accept that. Then Ostrom 1969 echoed Huxley’s hypothesis with new discoveries of Deinonychus. Still to little to no progress in the paleo community.
the Hartford Courant (2000), “In 1973, Ostrom broke from the scientific mainstream by reviving a Victorian-era hypothesis (see above) that his colleagues considered far-fetched: Birds, he said, evolved from dinosaurs. And he spent the rest of his career trying to prove it.” With the announcement of the first dinosaurs with feathers from China, Ostrom (then age 73) was in no mood to celebrate. He is quoted as saying, ““I’ve been saying the same damn thing since 1973, `I said, `Look at Archaeopteryx!’” Ostrom was the first scientist to collect physical evidence for the theory. Ostrom provoked a debate that raged for decades. “At first they said, `Oh John, you’re crazy,”’ Ostrom said in 1999.”
It wasn’t until dozens of Chinese specimens
appeared with feathers that paleontologists finally got out of their academic chairs and said in essence, ‘well, we better change our mind about feathers and dinosaurs, or else.’ The scaly theropods in the Jurassic Park/Jurassic World movies reflect that slow-to-accept mentality.
Books should not just echo false tripes
and recirculate untenable cladograms. Books should break old paradigms and advance new and valid ideas. Case in point: The Dinosaur Heresies by Bakker 1986.
Bakker RT 1986. The dinosaur heresies. New theories unlocking the mystery of the dinosaurs and their extinction. Citadel Press.
Brusatte S, Niedźwiedzki G and Butler RJ 2011. Footprints pull origin and diversification of dinosaur stem-lineage deep into Early Triassic. Proceedings of the Royal Society of London, Series B, 278, 1107-1113.
Brusatte S 2015. Rise of the Tyrannosaurs. Scientific American 312:34-41. doi:10.1038/scientificamerican0515-34
Brusatte S 2018. The rise and fall of the dinosaurs. Harper Academic. author interview
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Ostrom JH 1969. “Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana”. Peabody Museum of Natural History Bulletin. 30:1–165.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Wallace J 1987. The rise and fall of the dinosaur. Gallery Books
Weishampel DE and Fastovsky DB 2009: Dinosaurs: a concise natural history. 3 editions. Cambridge University Press. pdf