How has our knowledge of dinosaur diversity through geologic time changed through research history?

Abstract

Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abundance curve, which are largely dependent on databases compiled from the primary published literature. However, how these 'corrected' diversity patterns are influenced by the history of publication remains largely unknown. Here, we investigate the influence of publication history between 1991 and 2015 on our understanding of dinosaur evolution using raw diversity estimates and shareholder quorum subsampling for the three major subgroups: Ornithischia, Sauropodomorpha, and Theropoda. We find that, while sampling generally improves through time, there remain periods and regions in dinosaur evolutionary history where diversity estimates are highly volatile (e.g. the latest Jurassic of Europe, the mid-Cretaceous of North America, and the Late Cretaceous of South America). Our results show that historical changes in database compilation can often substantially influence our interpretations of dinosaur diversity. 'Global' estimates of diversity based on the fossil record are often also based on incomplete, and distinct regional signals, each subject to their own sampling history. Changes in the record of taxon abundance distribution, either through discovery of new taxa or addition of existing taxa to improve sampling evenness, are important in improving the reliability of our interpretations of dinosaur diversity. Furthermore, the number of occurrences and newly identified dinosaurs is still rapidly increasing through time, suggesting that it is entirely possible for much of what we know about dinosaurs at the present to change within the next 20 years.

Keywords: Cretaceous; Dinosaurs; Diversity; Extinction; Jurassic; Macroevolution; Mesozoic; Paleobiology Database; Publication bias; Triassic.

Figure 1. Frequency (A) and cumulative frequency (B) of newly published dinosaur occurrences through publication time.

Please note that all raw figure files (PDF) and the R code for generating these are available in Supplemental Information 10.

Figure 2. Frequency (A) and cumulative frequency (B) of newly published dinosaur genera through publication time.

Figure 3. The number of invalidated or revised dinosaur taxa between 1991 and 2015.

Figure 4. Total dinosaur ‘global’ diversity patterns for (A) raw and (B) subsampled data.

The vertical red lines represent major interval boundaries. Time stage abbreviations (in chronological order). N, Norian; R, Rhaetian, He, Hettangian; S, Sinemurian; P, Pliensbachian; T, Toarcian; A, Aalenian; Bj, Bajocian; B, Bathonian; C, Callovian; O, Oxfordian; K, Kimmeridgian; Ti, Tithonian; Be, Berriasian; V, Valanginian; Ha, Hauterivian; Ba, Barremian; Ap, Aptian; Al, Albian; Ce, Cenomanian; Tu, Turonian; Co, Coniacian; Sa, Santonian; Cam, Campanian; M, Maastrichtian. Vertical dashed red lines indicate boundaries between different periods (Triassic/Jurassic, Jurassic/Cretaceous, and Cretaceous/Paleogene).

Figure 5. Raw ornithischian diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 6. Subsampled ornithischian diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 7. Good’s u estimates for ornithischians at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 8. Raw theropod diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 9. Subsampled theropod diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 10. Good’s u estimates for theropods at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 11. Raw sauropodomorph diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 12. Subsampled sauropodomorph diversity at (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.

Figure 13. Good’s u estimates for sauropodomorphs at a (A) global and (B–F) regional levels (Europe, Africa, Asia, North America, and South America, respectively) based on our published knowledge in 1991 and 2015.

Abbreviations as Fig. 4.