4 Papers on dinosaur diversity

Question 1

Fastovsky et al. (2004)

Answer 1

Steadily increasing rate (upward curve) of diversification through mesozoic, reaching maximum at end-cretaceous, attributed to the development of new innovations and behavioural strategies allowing the radiation into more ecological niches.

No decrease in richness towards KT extinction event.

Suggests rate of extinction at KT boundary can be best estimated by more accurate dating of fossils, rather than collecting more fossils

Asia and North America dominate database (perhaps because this is where most fossil collection has occurred and data has been obtained, rather than purely more species occurring here, which may not even be the case).
Also time bins not of equal duration.

Question 2

Mesozoic =

Answer 2

triassic, jurassic and cretaceous

Question 3

Wang and Dodson (2006)

Answer 3

Estimates that at least 71% of dinosaur genera are currently unknown and yet to be described (using ACE statistical method).

General increasing trend in diversity through mesozoic, peaking in Late Cretaceous (this time accounting for future discoveries)

Although known diversity did decline in the last stage of the Cretaceous, Wang and Dodson estimate that dinosaur diversity was steady and not in decline 10my before their ultimate extinction. (apparent decline result of biased fossil record)

Acknowledge that diversity is biased by the availability of fossiliferous rock outcrop and fossil record is biased and incomplete, which effects known diversity through time (rock availability is correlated with known diversity)

Predict 75% of discoverable genera will be known within the next 100 years and 90% within the next 140

Middle Jurassic fossil record is poor and proposed to be missing the highest proportion of genera

Question 4

Lloyd et al. (2008)

Answer 4

Observed diversity reached peak during mid- and Late Cretaceous (50Myr prior to extinction) - but may be largely explained by sampling bias. Time bins were of ~equal duration.

Apparent burst of increasing dinosaur diversity in mid Cretaceous (previously suggested to be part of KTR - cretaceous terrestrial revolution) may also be a sampling artefact, despite coinciding with the emergence of new clades of medium to large herbivores and carnivores - originations did not correspond to significant diversification shifts. Dinosaur evolution was not driven by the KTR
- quantitative study of diversification applied to new supertree of dinosaurs

Major diversification shifts occurred largely in the first one-third of the group’s history

The cretaceous dinosaur phylogenetic tree follows the null hypothesis of an equal rates model of lineage branching

Again, no support for progressive decline in diversity at the end of the Cretaceous

Question 5

Barrett et al. (2009)

Answer 5

Genus-richness estimates for three Mesozoic dinosaur clades (Ornithischia, Sauropodomorpha, Theropoda) compiled. Created a linear model of amount of fossiliferous outcrop through time, using number of dinosaur-bearing formations as a proxy.

Comparing modelled diversity estimates with observed patterns demonstrated that almost all patterns of ornithischian and theropodan diversity could be explained by geological megabiases - strongly aligned with rock outcrop curves
- The sauropodomorph lineage, however, may be more accurately represented, as this diverged more from the modelled predictions - inferring diversification and evolutionary processes from this group may be more reliable

This study DID identify a marked decline in dinosaur genus richness towards the end of the Cretaceous period (prior to final extinction of non-avian dinosaurs)

Question 6

All studies mean …-… … when they say “dinosaurs”

Answer 6

non-avian