Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 106 (13), 5218-23

Ecomorphological Selectivity Among Marine Teleost Fishes During the end-Cretaceous Extinction

Affiliations

Ecomorphological Selectivity Among Marine Teleost Fishes During the end-Cretaceous Extinction

Matt Friedman. Proc Natl Acad Sci U S A.

Abstract

Despite the attention focused on mass extinction events in the fossil record, patterns of extinction in the dominant group of marine vertebrates-fishes-remain largely unexplored. Here, I demonstrate ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction, based on a genus-level dataset that accounts for lineages predicted on the basis of phylogeny but not yet sampled in the fossil record. Two ecologically relevant anatomical features are considered: body size and jaw-closing lever ratio. Extinction intensity is higher for taxa with large body sizes and jaws consistent with speed (rather than force) transmission; resampling tests indicate that victims represent a nonrandom subset of taxa present in the final stage of the Cretaceous. Logistic regressions of the raw data reveal that this nonrandom distribution stems primarily from the larger body sizes of victims relative to survivors. Jaw mechanics are also a significant factor for most dataset partitions but are always less important than body size. When data are corrected for phylogenetic nonindependence, jaw mechanics show a significant correlation with extinction risk, but body size does not. Many modern large-bodied, predatory taxa currently suffering from overexploitation, such billfishes and tunas, first occur in the Paleocene, when they appear to have filled the functional space vacated by some extinction victims.

Conflict of interest statement

The author declares no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Extinction victims and survivors considered by this analysis. Bold black lines represent genus-level lineages, whereas finer gray lines indicate phylogenetic relationships. The vertical axis represents time (K/P indicates Cretaceous/Paleogene boundary), whereas the horizontal axis corresponds to variation in a hypothetical trait value. The first 2 lineages represent the only groups typically incorporated by studies of fossil data: taxa that make their last appearance in the interval preceding the horizon of interest (observed victim) and those that appear on both sides of the horizon (observed survivor). Phylogenies can imply further, unsampled, boundary-crossing lineages, but these are rarely considered. Trait values for inferred survivors are estimated here by using both punctuated (on the left) and gradual (on the right) models of trait evolution.
Fig. 2.
Fig. 2.
Distribution of marine teleost survivors (open triangles, blue envelope) and victims (filled circles, red envelope) of the end-Cretaceous extinction, showing the effect of excluding some dataset partitions (vertical axis) and different models of character evolution used to estimate trait values for inferred boundary-crossing lineages (horizontal axis). The distribution of survivors and victims is significantly different regardless of these permutations (significance indicated in upper right-hand corner of the plots). The number of genera is indicated in the lower left-hand corner of the plots; the figure in parentheses indicates the number of victims. Dataset partitions are as follows: Nardò: taxa making their last appearance in the imprecisely dated Nardò fossil assemblage; Recent, boundary crossing lineages inferred on the basis of extant taxa alone (i.e., no Cenozoic body fossil record).
Fig. 3.
Fig. 3.
Jaws belonging to victims that fall outside the envelope of survivors in all data partitions (see Fig. 2). (A) †Belonostomus. (B) †Protosphyraena. (C) †Xiphactinus. (D) †Saurodon. (E) †Saurocephalus. (F) †Pachyrhizodus. (G) †Pentanogmius. (H) †Apateodus. (I) †Cimolichthys. (J) †Enchodus. Jaws marked with an asterisk are from taxa where gut contents from that genus or a closely related form indicate predation on large, nektonic prey (SI Appendix; see also Dataset S1 for unprocessed measurements). Measurements used to calculate jaw closing mechanical advantage (input lever: LI; output lever: LO; MA = LI/LO) are shown in F. Predentary bones of †Saurodon and †Saurocephalus were not used in calculations of MA, and are shown in light gray here. Images are not to the same scale.
Fig. 4.
Fig. 4.
Independent contrasts for body size and MA, showing shifts in these traits for extinction victims (either individual genera or higher clades) relative to their nearest surviving relatives. Patterns recovered from analyses of phylogenetically uncorrected data predict that points should be clustered in the shaded quadrant (i.e., victims should have larger body sizes and lower MA values). Shifts are significantly biased toward decreased MA for both datasets (gradual, P = 0.011; punctuated, P = 0.022; one-tailed t test), but neither demonstrates a significant bias in body-size shifts (gradual, P = 0.19; punctuated, P = 0.51; one-tailed t test).

Similar articles

See all similar articles

Cited by 32 PubMed Central articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback