Lauren Sallan

Okinawa Institute of Science and Technology | OIST · Marine Macroevolution Unit

Predator-prey interactions are thought by many researchers to define both modern ecosystems and past macroevolutionary events. In modern ecosystems, experimental removal or addition of taxa is often used to determine trophic relationships and predator identity. Both characteristics are notoriously difficult to infer in the fossil record, where evid...

Adaptive radiations, bouts of morphological divergence coupled with taxonomic proliferation, underpin biodiversity. The most widespread model of radiations assumes a single round, or 'early burst', of elevated phenotypic divergence followed by a decline in rates of change or even stasis. A vertebrate-specific model proposes separate stages: initial...

Following the end-Devonian mass extinction (359 million years ago), vertebrates experienced persistent reductions in body size for at least 36 million years. Global shrinkage was not related to oxygen or temperature, which suggests that ecological drivers played a key role in determining the length and direction of size trends. Small, fast-breeding...

Shallow-water diversification Most of what we know about the relationship between diversification and environment in ancient marine environments has come from invertebrates. The influence of habitat on vertebrate diversification thus remains a persistent question. Sallan et al. studied fossil vertebrates spanning the mid-Paleozoic, including both j...

The symmetrical, flexible teleost fish ‘tail’ has been a prime example of recapitulation — evolutionary change (phylogeny) mirrored in development (ontogeny). Paleozoic ray-finned fishes (Actinopterygii), relatives of teleosts, exhibited ancestral scale-covered tails curved over their caudal fins. For over 150 years, this arrangement was thought to...

Solid vertebrae evolved multiple times across vertebrates, but the origins and relationships of different spine forms remain unclear. A new study reveals teleost fishes evolved their solid vertebrae following genome duplication, when a novel gene repressed ancestral spine programming.

The Carboniferous radiation of fishes was marked by the convergent appearance of then-novel but now common ecomorphologies resulting from changes in the relative proportions of traits, including elongation of the front of the skull (rostrum). The earliest ray-finned fishes (Actinopterygii) with elongate rostra are poorly known, obscuring the earlie...

We surveyed the taxa, ecosystems, and localities of the Devonian fishes of Michigan to provide a framework for renewed study, to learn about the diversity and number of these fishes, and to investigate their connection to other North American faunas. Nineteen genera of fishes have been found in the Middle and Late Devonian deposits of Michigan, of...

Vertebrate bearing localities from the Alpena Limestone, Four Mile Dam Formation, Norway Point Formation, and Potter Farm Formation

Vertebrate bearing localities from Dundee Limestone, Bell Shale, and Rockport Quarry Limestone

Examined specimens in Michigan museum collections

Vertebrate bearing localities from the Thunder Bay Limestone and the Antrim Shale

Vertebrate bearing localities from the Genshaw Formation, Newton Creek Limestone, Gravel Point Formation, and Alpena Limestone

Faunal lists for Devonian fish localities from Michigan

Far more species of organisms are found in the tropics than in temperate and polar regions, but the evolutionary and ecological causes of this pattern remain controversial1,2. Tropical marine fish communities are much more diverse than cold-water fish communities found at higher latitudes3,4, and several explanations for this latitudinal diversity...

The affinity of Tullimonstrum gregarium, a pincer-mouthed, soft bodied bilaterian, has been subject to debate since its recovery from Carboniferous coal deposits at Mazon Creek, Illinois. After decades of impasse focused on mollusc, arthropod and annelid attributes, two recent, yet conflicting, high-profile studies concluded that the ‘Tully Monster...

Bowfin belongs to an ancient lineage of nonteleost ray-finned fishes (actinopterygians) and is the only extant survivor of a once diverged group, the Halecomorphi or Amiiformes. Owing to the scarcity of extant nonteleost ray-finned lineages, also referred as "living fossils," their phylogenetic interrelationships have been the target of multiple hy...

Ray-finned fishes (Actinopterygii) dominate modern aquatic ecosystems and are represented by over 32000 extant species. The vast majority of living actinopterygians are teleosts; their success is often attributed to a genome duplication event or morphological novelties. The remainder are 'living fossils' belonging to a few depauperate lineages with...

The shark Bandringa (Elasmobranchii, Chondrichthyes), from the Pennsylvanian (Moscovian) Lagerstätte of Mazon Creek, Illinois, is notable for an elongated snout constituting up to half of total body length. This genus formerly contained two distinct species (B. rayi and B. herdinae). However, reexamination of all cataloged material from Mazon Creek...

The Carboniferous fish family Styracopteridae (Actinopterygii) originated as part of the initial radiation of ray-finned fishes following the end-Devonian Hangenberg extinction. Specimens of Styracopterus fulcratus (Traquair, 1890) have been collected from post-extinction Tournaisian and Visean Scottish sediments for over 100 years, including sites...

Fishes include more than half of all living animals with backbones, but large-scale palaeobiological patterns in this assemblage have not received the same attention as those for terrestrial vertebrates. Previous surveys of the fish record have generally been anecdotal, or limited either in their stratigraphic or in their taxonomic scope. Here, we...

Tetrapods possess up to five morphologically distinct vertebral series: cervical, thoracic, lumbar, sacral and caudal. The evolution of axial regionalization has been linked to derived Hox expression patterns during development and the demands of weight-bearing and walking on land. These evolutionary and functional explanations are supported by an...

The Devonian marks a critical stage in the early evolution of vertebrates: It opens with an unprecedented diversity of fishes and closes with the earliest evidence of limbed tetrapods. However, the latter part of the Devonian has also been characterized as a period of global biotic crisis marked by two large extinction pulses: a "Big Five" mass ext...