Evolution and Diversification of Delphinid Skull Shapes

Abstract

Summary The diversity of the dolphin family was established during a short window of time. We investigated delphinid skull shape evolution, mapping shapes on an up-to-date nuclear phylogeny. In this model, the common ancestor was similar to Lagenorhynchus albirostris . Initial diversification occurred in three directions: toward specialized raptorial feeders of small prey with longer, narrower beaks, e.g., Delphinus ; toward wider skulls with downward-oriented rostra and reduced temporal fossae, exemplified by suction feeders, e.g., Globicephala; and toward shorter and wider skulls/rostra and enlarged temporal fossae, e.g., Orcinus . Skull shape diversity was established early, the greatest later developments being adaptation of Steno to raptorial feeding on large prey and the convergence of Pseudorca toward Orcinus , related to handling large prey. Delphinid skull shapes are related to feeding mode and prey size, whereas adaptation to habitat is not marked. Over a short period, delphinid skulls have evolved a diversity eclipsing other extant odontocete clades.

Head adaptation for sound production and feeding strategy in dolphins (Odontoceti: Delphinida)

“…CF, centroid frequency; SL, source level; NBHF, narrow‐band high‐frequency, SW, sperm whale; BB, broad‐band; FM, frequency‐modulated. Feeding strategy classification followed Werth (2006), Johnston and Berta (2011) and Galatius et al (2020): octagon, raptorial; square, combination; triangle, suction…”

“…Combined with a complex socio‐cultural development (Fox et al, 2017), these features might explain, in part, their increased success in the marine environment (Kaschner et al, 2011; Pyenson, 2017). On the other hand, suction or raptorial feeding specialists seem to present prey specific preferences (McCurry et al, 2017) which may have driven the evolution of skull morphology (Galatius et al, 2020). Thus, it would be plausible to assume distinct sound modulation strategies to hunt prey with characteristic sound reflection properties (e.g., squid vs. fish).…”

“…CF, centroid frequency; SL, source level; NBHF, narrow-band high-frequency, SW, sperm whale; BB, broad-band; FM, frequency-modulated. Feeding strategy classification followedWerth (2006),Johnston and Berta (2011) andGalatius et al (2020): octagon, raptorial; square, combination; triangle, suction TA B L E 2 Attribute differences (d), standardized scores (Z), and p-values (p) for skull and mandible trajectories. Significant values are indicated in bold.…”

Deathly Silent: Exploring the Global Lack of Data Relating to Stranded Cetacean Euthanasia

“…This further supports the notion that additional work on euthanasia methods is required in order to ensure that the most appropriate method and associated equipment are used for the species in question. In terms of ballistics, this should include ballistics trials on cadavers to ensure the most appropriate approach, firearm and projectile are employed, particularly in relation to the varying skull morphology between species [59]. For chemical euthanasia, this should include detailed documentation of the chemical agent and associated sedatives used, along with details of the needle gauge, dosages and any behavioural reaction that may occur [17].…”

A new protocetid whale offers clues to biogeography and feeding ecology in early cetacean evolution

“…(c) Craniomandibular morphology and musculature One of the key features seen in the cranium of Phiomicetus is the enlarged temporal fossa, occupying most of the lateral surface of the neurocranium. The size of the temporal fossa is a powerful predictor of the size and efficiency of the temporalis musculature [31][32][33][34]. A relatively large temporal fossa in Phiomicetus would have been occupied by relatively large muscles of mastication with larger cross-sectional areas and increased capacity for powerful bite force, presumably representing an adaptation for raptorial feeding on larger prey [31][32][33].…”