Faviel Alejandro López Romero

University of Vienna | UniWien · Institut für Paläontologie

Elasmobranchs (sharks, rays, skates) are a very successful group of cartilaginous fishes that have originated more than 400 million of years ago, survived almost all major extinction events and constantly occupied higher positions in past environments. It is possible to quantify their obvious evolutionary success using their long evolutionary persi...

Elasmobranchs form a highly diversified monophyletic clade of marine vertebrates comprising all living sharks, rays, and skates, as well as their immediate fossil relatives. Within crowngroup elasmobranchs, two major shark groups, the Galeomorphii and the Squalomorphii, are repeatedly supported by molecular evidence, and with more than 290 extant s...

Environmental controls of species diversity represent a central research focus in evolutionary biology. In the marine realm, sharks are widely distributed, occupying mainly higher trophic levels and varied dietary preferences, mirrored by several morphological traits and behaviours. Recent comparative phylogenetic studies revealed that sharks prese...

The Late Jurassic-Early Cretaceous (164–100 Ma) represents one of the main transitional periods in life history. Recent studies unveiled a complex scenario in which abiotic and biotic factors and drivers on regional and global scales due to the fragmentation of Pangaea resulted in dramatic faunal and ecological turnovers in terrestrial and marine e...

The lifelong tooth replacement in elasmobranch fishes (sharks, rays and skates) has led to the assemblage of a great number of teeth from fossil and extant species, rendering tooth morphology an important character for taxonomic descriptions, analysing phylogenetic interrelationships and deciphering their evolutionary history (e.g. origination, div...

Background The onset of morphological differences between related groups can be tracked at early stages during embryological development. This is expressed in functional traits that start with minor variations, but eventually diverge to defined specific morphologies. Several processes during this period, like proliferation, remodelling, and apoptos...

Every night the greatest migration on Earth starts in the deep pelagic oceans where organisms move up to the meso-and epipelagic to find food and return to the deeper zones during the day. One of the dominant fish taxa undertaking vertical migrations are the dragonfishes (Stomiiformes). However, the functional aspects of locomotion and the architec...

Asteracanthus was one of the most common Mesozoic hybodontiform chondrichthyans, given that remains traditionally referred to this genus have been reported almost worldwide from Middle Triassic to Late Cretaceous strata so far. Asteracanthus was erected by Louis Agassiz for Late Juras-sic fin spines with stellate tubercles. Later, Arthur Smith Wood...

The diversity of skeletal tissues in extant vertebrates includes mineralized and unmineralized structures made of bone, cartilage, or tissues of intermediate nature. This variability, together with the diverse nature of skeletal tissues in fossil species question the origin of skeletonization in early vertebrates. In particular, the study of skelet...

Sharks have a long and rich fossil record that consists predominantly of isolated teeth due to the poorly mineralized cartilaginous skeleton. Tiger sharks (Galeocerdo), which represent apex predators in modern oceans, have a known fossil record extending back into the early Eocene (ca. 56 Ma) and comprise 22 recognized extinct and one extant specie...

Pycnodontiformes was a successful lineage of primarily marine fishes that broadly diversified during the Mesozoic. They possessed a wide variety of body shapes and were adapted to a broad range of food sources. Two other neopterygian clades possessing similar ecological adaptations in both body morphology (†Dapediiformes) and dentition (Ginglymodi)...

elasmobranchii (i.e., sharks, skates, and rays) forms one of the most diverse groups of marine predators. With a fossil record extending back into the Devonian, several modifications in their body plan illustrate their body shape diversity through time. the angel sharks, whose fossil record dates back to the Late Jurassic, some 160 Ma, have a dorso...

Chlamydoselachus anguineus, Garman 1884, commonly called the frilled shark, is a deep sea shark species occurring up to depths of 1300 m. It is assumed to represent an ancient morphotype of sharks (e.g., terminal mouth opening, more than five gill slits) and thus is often considered to represent plesiomorphic traits for sharks. Therefore, its early...

Sharks of the order Lamniformes comprise seven families with 15 extant species, including some of the most iconic shark species, like the great white shark (Carcharodon carcharias) and †Otodus megalodon. Lamniform sharks have a rich fossil record dating back to the Cretaceous with the oldest confirmed members of this group being known from the Barr...

The fossil record of modern sharks mainly consists of isolated teeth due to their poorly mineralized cartilaginous endoskeleton and a continuous tooth replacement that forms thousands of teeth during a sharks' lifetime. As a result, phylogenetic analyses of extinct shark taxa are mostly based on isolated teeth and therefore often lead to ambiguous...

Elasmobranchii (i.e., sharks, skates, and rays) constitute a speciose group of chondrichthyan fishes, ranging back to the Permian. They form, together with extinct hybodontiform shark-like chondrichthyans, their supposed sister group ranging from the Devonian to the end of the Cretaceous, the most dominant chondrichthyan lineage during the Mesozoic...

The Early Jurassic represents a crucial time interval in the evolutionary history of elasmobranchs, because the Toarcian witnessed a first major diversification, suggesting a profound reorganization of ecological niches of chondrichthyans, probably accompanied by a subsequent diversity decline of hybodontiforms within marine environments. Potential...

The cartilaginous fishes (Chondrichthyes) have a rich fossil record which consists mostly of isolated teeth and, therefore, phylogenetic relationships of extinct taxa are mainly resolved based on dental characters. One character, the tooth histology, has been examined since the 19th century, but its implications on the phylogeny of Chondrichthyes i...

Extant sharks of the order Lamniformes show a relatively low taxonomic diversity (15 species) but display a remarkably varied and specialised set of morphological and ecological traits (high ecomorphological disparity). This reflects the evolutionary history of this group, which diversified and flourished through the Cretaceous and Paleogene (145 m...

Bilaterally symmetric organisms display mirror copies of their structures on both sides of the body, and the development of both sides is regulated by the same set of genes. Environmental variations can directly affect phenotype, and exposure to chemical contaminants at certain stages may modify embryonic development. The pesticide sodium pentachlo...

Río Champotón in the Yucatán Peninsula is within the Usumacinta Province, the most diverse in fish fauna in Mexico, and is part of the Mesoamerican hotspot, with high endemism and exceptional habitat loss. The spatial and seasonal variability of its fish fauna and their relation to physical habitat characteristics were studied, finding 53 taxa. Can...