Coelacanth jaw muscles re-identified

Datovo and Johnson 2025
just prepared a study on coelacanth (Latimeria, Fig 1) skull and jaw muscles, re-identifying and re-classifying most of the soft elements.

Figure 2. Actinistia origins and phylogeny. The outgroup here is Parasemionotus and basal taxa are not lobefins. ” data-image-caption=”

Figure 2. Actinistia origins and phylogeny. The outgroup here is Parasemionotus and basal taxa are not lobefins.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/02/actinistia_phylogeny588-3.jpg?w=53″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/02/actinistia_phylogeny588-3.jpg?w=182″ class=”size-full wp-image-84437″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/02/actinistia_phylogeny588-3.jpg” alt=”Figure 2. Actinistia origins and phylogeny. The outgroup here is Parasemionotus and basal taxa are not lobefins.” width=”584″ height=”3289″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/02/actinistia_phylogeny588-3.jpg?w=584&h=3289 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/02/actinistia_phylogeny588-3.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Actinistia origins and phylogeny. The outgroup here is Parasemionotus and basal taxa are not lobefins.

The authors reported in the publicity,
“Upon re-examining the cranial musculature of the African coelacanth (Latimeria chalumnae), the authors discovered that only 13% of the previously identified evolutionary muscle novelties for the largest vertebrate lineages were accurate. The study also identified nine new evolutionary transformations related to innovations in feeding and respiration in these groups.”

“Ultimately, it’s even more similar to cartilaginous fish [sharks, rays, and chimaeras] and tetrapods [birds, mammals, amphibians, and reptiles] than previously thought. And even more distinct from ray-finned fish, which make up about half of living vertebrates,” says Aléssio Datovo, a professor at the Museum of Zoology (MZ) at USP supported by FAPESP, who led the study.”

“Among the evolutionary novelties erroneously identified as present in coelacanths are muscles responsible for actively expanding the buccopharyngeal cavity, which extends from the mouth to the pharynx. This set of muscles is directly related to food capture and respiration. However, the study showed that these supposed muscles in coelacanths were actually ligaments, which are structures incapable of contraction.”

“The sarcopterygii include fish such as coelacanths and lungfish, as well as all other tetrapods, because they evolved from an aquatic ancestor. These include mammals, birds, reptiles, and amphibians.”

Undone by taxon exclusion. In the large reptile tree (LRT, 2338 taxa, subset Fig 2) deep-sea, deep-bodied coelacanths are not related to near-shore, wide-bodied, air-breathing lungfish and pre-tetrapod fish.

“In ray-finned fish, such as aquarium carp, it is easy to see how the mouth moves to suck in food. This is a fundamental difference from other fish, such as coelacanths and sharks, which primarily feed by biting their prey.”

This statement indicates a naive understanding of fish jaws (Fig 3). Biters and suckers appear and disappear by convergence in the several bony fish and several gnathostome clades in the LRT (Fig 2). The LRT does not recover simple separate clades of biters vs suckers.

Figure 2. Subset of the LRT focusing on fish. Here suckers are in olive green, biters are light red, nibblers are in light blue and engulfers are in tan. ” data-image-caption=”

Figure 2. Subset of the LRT focusing on fish. Here suckers are in olive green, biters are light red, nibblers are in light blue and engulfers are in tan.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg?w=109″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg?w=373″ class=”size-full wp-image-94122″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg” alt=”Figure 2. Subset of the LRT focusing on fish. Here suckers are in olive green, biters are light red, nibblers are in light blue and engulfers are in tan.” width=”584″ height=”1605″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg?w=584&h=1605 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg?w=55&h=150 55w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg?w=109&h=300 109w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/biters-suckers588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Subset of the LRT focusing on fish. Here suckers are in olive green, biters are light red, nibblers are in light blue and engulfers are in tan. Apologies for the tiny type.

The cladogram published by Datovo and Johnson
(Fig 3) includes too few taxa to recover several origins of jaws and too few taxa to separate coelacanths from lungfish + pre-tetrapods.

Figure 3. Cladogram by Datovo and Johnson 2025 includes too few taxa to split the several origins of jaw and to split deep-bodied coelacanths from convergent wide-boided lobefins that gave rise to air-breathing tetrapods. ” data-image-caption=”

Figure 3. Cladogram by Datovo and Johnson 2025 includes too few taxa to split the several origins of jaw and to split deep-bodied coelacanths from convergent wide-boided lobefins that gave rise to air-breathing tetrapods.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg?w=584″ class=”size-full wp-image-94124″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg” alt=”Figure 3. Cladogram by Datovo and Johnson 2025 includes too few taxa to split the several origins of jaw and to split deep-bodied coelacanths from convergent wide-boided lobefins that gave rise to air-breathing tetrapods.” width=”584″ height=”549″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg?w=584&h=549 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg?w=150&h=141 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg?w=300&h=282 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/08/coelocanth.cladogram588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 3. Cladogram by Datovo and Johnson 2025 includes too few taxa to split the several origins of jaw and to split deep-bodied coelacanths from convergent wide-boided lobefins that gave rise to air-breathing tetrapods. Yellow taxa are related in the LRT. So are blue taxa.

From the Datovo and Johnson 2025 abstract:
“Coelacanths are rare fishes that occupy a key evolutionary position in the vertebrate tree of life. Despite being exhaustively studied, we found that a substantial part of the knowledge on their cranial musculature was mistaken. Eleven previously reported coelacanth “muscles” are nonexistent, while three previously unknown muscle subdivisions and connections are found. These findings markedly affect our understanding of the deep-time cranial evolution of jawed vertebrates (gnathostomes).

The authors have not tested enough taxa (Fig 3) to understand the several origins of jawed vertebrates.

“Only 13% of the previously identified myological evolutionary novelties for the major gnathostome lineages proved to be accurate, but several new ones are proposed. We show that low, moderate, and high levels of cranial muscle innovation characterized the emergence of lobe-finned (sarcopterygian), cartilaginous (chondrichthyan), and ray-finned (actinopterygian) fishes, respectively.”

“The novelties in the latter group resulted in the evolution of a second active mechanism for the expansion of the oropharyngeal cavity, which was probably crucial for the predominance of suction feeding versus bite feeding in extant actinopterygians.”

The authors have not tested enough taxa (Fig 3) to understand the several convergent origins (Fig 2) of biters and suction-feeding fishes.

References
Datovo A and Johnson G 2025. Coelacanths illuminate deep-time evolution of cranial musculature in jawed vertebrates. Science Advances May 2;11(18):eadt1576. doi: 10.1126/sciadv.adt1576. Epub 2025 Apr 30

Publicity
Fundação de Amparo à Pesquisa do Estado de São Paulo. “400-million-year-old fish exposes big mistake in how we understood evolution.” ScienceDaily. sciencedaily.com, 29 July 2025.

earth.com
“Living Fossil” Just Shattered 70 Years of Evolutionary Assumptions”