The fossil record of fish ontogenies: Insights into developmental patterns and processes

The revival of a so-called rotten fish: the ontogeny of the Devonian acanthodian Triazeugacanthus

“…What was considered as the progressive disappearance of fin spines, scales, cranial and girdle bony elements corresponds in fact to the sequential appearance of these elements, primarily as a sequence of skeletal formation. The shape of the cumulative curve of elements is similar to 'maturity curves' or 'ontogenetic trajectories' in living [20] and extinct fishes [11]. The postero-anterior direction of squamation development in Triazeugacanthus is also congruent with that observed for other acanthodians and some actinopterygians [11,21]; it would be unlikely for scales or patches of scales to be lost in a non-random pattern (detached scales were found in the abdominal region as a result of decay).…”

“…Recently, Cloutier et al [10] and Cloutier [11] agreed with this interpretation based on shape morphometry and squamation pattern. However, this ontogenetic interpretation has to be quantitatively tested on a large number of specimens.…”

“…Based on the squamation extent and pattern, ossification completion and allometry, the three morphotypes are best interpreted as three ontogenetic stages making this growth series one of the best documented early gnathostome fossilized ontogenies [10,11]. Morph-1 showing no body squamation corresponds to a larval stage [10,11,16]; morph-2 starts with the initiation of squamation and shows allometry, which is characteristic of a juvenile stage [10,11,17]; and the completion of squamation and ossification characterising morph-3 corresponds to an adult stage [11]. The evidence for ontogeny in Triazeugacanthus that we have presented does not rule out taphonomic alteration but shows that the main trend of variation is explained by ontogenetic changes.…”

Ornamentation of dermal bones of Placodermi from the Lower Devonian of Morocco as a measure of biodiversity

“…Size and shape of the plates may differ between ontogenetic stages (Cloutier, 2010;Trinajstic & Hazelton, 2007). Trinajstic & McNamara (1999) described variation in allometry during ontogeny in Compagopiscis croucheri, thus showing that characters previously assumed to represent taxonomic distinctness between C. croucheri and Gogopiscis gracilis are in fact greatest morphological changes during ontogeny of a single species.…”

A case study of developmental palaeontology in <i>Stereosternum tumidum</i> (Mesosauridae, Parareptilia)

“…If preserved, they provide valuable insight into the life history of extinct taxa, as well as evolutionary trajectories. To date, ossification sequences in fossils are available for some "fish" (Cloutier, 2010), temnospondyl and lepospondyl amphibians (Fröbisch, 2008;Fröbisch et al, 2010Fröbisch et al, , 2015, "younginiforms" (sensu Bickelmann et al, 2009) (Currie, 1981;Caldwell, 2002), mosasaurs (Caldwell, 2002), sauropterygians (Hugi and Scheyer, 2012), ichthyosaurs (Caldwell, 1997), sauropsids (Delfino and Sánchez-Villagra, 2010) and mammals (Sánchez-Villagra, 2010). Most of this information is derived from secondarily aquatic taxa, which is the result of a taphonomic bias (Fröbisch et al, 2010).…”