A report in the journal Current Biology on July 9 offers a detailed description of the first nearly complete skeleton of an extinct large dolphin, discovered in what is now South Carolina. The 15-foot-long dolphin (Ankylorhiza tiedemani comb. n.) lived during the Oligocene — about 25 million years ago — and was previously known only from a partial rostrum (snout) fossil.

The researchers say that multiple lines of evidence — from the skull anatomy and teeth, to the flipper and vertebral column — show that this large dolphin (a toothed whale in the group Odontoceti) was a top predator in the community in which it lived. They say that many features of the dolphin’s postcranial skeleton also imply that modern baleen whales and modern toothed whales must have evolved similar features independently, driven by parallel evolution in the very similar aquatic habitats in which they lived.

“The degree to which baleen whales and dolphins independently arrive at the same overall swimming adaptations, rather than these traits evolving once in the common ancestor of both groups, surprised us,” says Robert Boessenecker of the College of Charleston in Charleston, South Carolina. “Some examples include the narrowing of the tail stock, increase in the number of tail vertebrae, and shortening of the humerus (upper arm bone) in the flipper.

“This is not apparent in different lineages of seals and sea lions, for example, which evolved into different modes of swimming and have very different looking postcranial skeletons,” he adds. “It’s as if the addition of extra finger bones in the flipper and the locking of the elbow joint has forced both major groups of cetaceans down a similar evolutionary pathway in terms of locomotion.”

Though first discovered in the 1880s from a fragmentary skull during phosphate dredging of the Wando River, the first skeleton of Ankylorhiza was discovered in the 1970s by then Charleston Museum Natural History curator Albert Sanders. The nearly complete skeleton described in the new study was found in the 1990s. A commercial paleontologist by the name of Mark Havenstein found it during construction of a housing subdivision in South Carolina. It was subsequently donated to the Mace Brown Museum of Natural History, to allow for its study.

While there’s much more to learn from this fossil specimen, the current findings reveal that Ankylorhiza was an ecological specialist. The researchers say the species was “very clearly preying upon large-bodied prey like a killer whale.”

Another intriguing aspect, according to the researchers, is that Ankylorhiza is the first echolocating whale to become an apex predator. When Ankylorhiza became extinct by about 23 million years ago, they explain, killer sperm whales and the shark-toothed dolphin Squalodon evolved and reoccupied the niche within 5 million years. After the last killer sperm whales died out about 5 million years ago, the niche was left open until the ice ages, with the evolution of killer whales about 1 or 2 million years ago.

“Whales and dolphins have a complicated and long evolutionary history, and at a glance, you may not get that impression from modern species,” Boessenecker says. “The fossil record has really cracked open this long, winding evolutionary path, and fossils like Ankylorhiza help illuminate how this happened.”

Boessenecker notes that more fossils of Ankylorhiza are awaiting study, including a second species and fossils of Ankylorhiza juveniles that can offer insight into the dolphin’s growth. He says that there’s still much to learn from fossilized dolphins and baleen whales from South Carolina.

“There are many other unique and strange early dolphins and baleen whales from Oligocene aged rocks in Charleston, South Carolina,” Boessenecker says. “Because the Oligocene epoch is the time when filter feeding and echolocation first evolved, and since marine mammal localities of that time are scarce worldwide, the fossils from Charleston offer the most complete window into the early evolution of these groups, offering unparalleled evolutionary insight.”

Reference:
Robert W. Boessenecker, Morgan Churchill, Emily A. Buchholtz, Brian L. Beatty, Jonathan H. Geisler. Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina. Current Biology, 2020; DOI: 10.1016/j.cub.2020.06.012

Note: The above post is reprinted from materials provided by Cell Press.

A PhD student has produced the first digital reconstruction of the skull of a gigantic dormouse, which roamed the island of Sicily around two million years ago.

In a new study, the student from Hull York Medical School, has digitally pieced together fossilised fragments from five giant dormouse skulls to reconstruct the first known complete skull of the species.

The researchers estimate that the enormous long-extinct rodent was roughly the size of a cat, making it the largest species of dormouse ever identified.

The digitally reconstructed skull is 10 cm long — the length of the entire body and tail of many types of modern dormouse.

PhD student Jesse Hennekam said: “Having only a few fossilised pieces of broken skulls available made it difficult to study this fascinating animal accurately. This new reconstruction gives us a much better understanding of what the giant dormouse may have looked like and how it may have lived.”

The enormous prehistoric dormouse is an example of island gigantism — a biological phenomenon in which the body size of an animal isolated on an island increases dramatically.

The palaeontological record shows that many weird and wonderful creatures once roamed the Italian islands. Alongside the giant dormouse, Sicily was also home to giant swans, giant owls and dwarf elephants.

Jesse’s PhD supervisor, Dr Philip Cox from the Department of Archaeology at the University of York and Hull York Medical School, said: “While Island dwarfism is relatively well understood, as with limited resources on an island animals may need to shrink to survive, the causes of gigantism are less obvious.

“Perhaps, with fewer terrestrial predators, larger animals are able to survive as there is less need for hiding in small spaces, or it could be a case of co-evolution with predatory birds where rodents get bigger to make them less vulnerable to being scooped up in talons.”

Jesse spotted the fossilised fragments of skull during a research visit to the Palermo Museum in Italy, where a segment of rock from the floor of a small cave, discovered during the construction of a motorway in northwest Sicily in the 1970s, was on display.

“I noticed what I thought were fragments of skull from an extinct species embedded in one of the cave floor segments,” Jesse said. “We arranged for the segment to be sent to Basel, Switzerland for microCT scanning and the resulting scans revealed five fragmented skulls of giant dormice present within the rock.”

The reconstruction is likely to play an important role in future research directed at improving understanding of why some small animals evolve larger body sizes on islands, the researchers say.

“The reconstructed skull gives us a better sense of whether the giant dormouse would have looked similar to its normal-sized counterparts or whether its physical appearance would have been influenced by adaptations to a specific environment,” Jesse explains.

“For example, if we look at the largest living rodent — the capybara — we can see that it has expanded in size on a different trajectory to other species in the same family.”

Jesse is also using biomechanical modelling to understand the feeding habits of the giant dormouse.

“At that size, it is possible that it may have had a very different diet to its smaller relatives,” he adds.

Reference:
Jesse J. Hennekam, Victoria L. Herridge, Loïc Costeur, Carolina Di Patti, Philip G. Cox. Virtual Cranial Reconstruction of the Endemic Gigantic Dormouse Leithia melitensis (Rodentia, Gliridae) from Poggio Schinaldo, Sicily. Open Quaternary, 2020; 6 DOI: 10.5334/oq.79

Note: The above post is reprinted from materials provided by University of York.

Hauffiopteryx altera (Latin for different from) has been identified as a new species of Ichthyosaurs by researchers from McGill University and the State Museum of Natural History Stuttgart in Germany.

Ichthyosaurs (‘fish lizards’), a group of tuna-shaped reptiles that inhabited Earth’s seas during the Mesozoic Era, were discovered by scientists in the early 19th century. Similar to the modern-day dolphin, ichthyosaurs underwent profound adaptions to aquatic environments including limbs transformed into flippers, a dorsal fin, and a tail fin.

Following a meticulous study of all specimens related to Hauffiopteryx typicus, a small 2-meter-long species, it was revealed that a single specimen in Germany was in fact different.

“Although the marine ecosystems are generally similar across Europe during this time, we are finding there are some rare and possibly endemic species,” explains Dirley Cortés, a graduate student under the supervision of Prof. Hans Larsson at McGill’s Redpath Museum and co-author of the study published in Palaeontologica Electronica. “This finding will have a lot to say about how these ancient ecosystems functioned.”

The fossils were retrieved in the Posidonia Shale, an Early Jurassic geological formation located at the axis of Austria, the Czech Republic, Germany, Luxembourg, the Netherlands and Switzerland. Quarried for over 200 years, the site has yielded thousands of spectacularly preserved ichthyosaur skeletons ranging between two and more than ten meters in length and representing seven species. Fossilized soft tissues, stomach contents and embryos were also discovered.

“We were surprised to discover that this small dolphin-sized specimen, collected decades ago, is a new species,” remarked Erin Maxwell, curator of fossil aquatic vertebrates at the State Museum of Natural History Stuttgart and lead author of the study. “There is quite a lot of diversity still waiting to be discovered in our vast museum collections.”

Reference:
Erin Maxwell et al. A revision of the Early Jurassic ichthyosaur Hauffiopteryx (Reptilia: Ichthyosauria), and description of a new species from southwestern Germany, Palaeontologia Electronica (2020). DOI: 10.26879/937

Note: The above post is reprinted from materials provided by McGill University.

Sturgeon, a long-lived, bottom-dwelling fish, are often described as “living fossils,” owing to the fact that their form has remained relatively constant, despite hundreds of millions of years of evolution.

In a new study in the Zoological Journal of the Linnean Society, researchers led by Jack Stack, a 2019 University of Pennsylvania graduate, and paleobiologist Lauren Sallan of Penn’s School of Arts & Sciences, closely examine the ancient fish species Tanyrhinichthys mcallisteri, which lived around 300 million years ago in an estuary environment in what is today New Mexico. Although they find the fish to be highly similar to sturgeons in its features, including its protruding snout, they show that these characteristics evolved in a distinct evolutionary path from those species that gave rise to modern sturgeons.

The find indicates that, although ancient, the features that enabled Tanyrhinichthys to thrive in its environment arose multiple times in different fish lineages, a burst of innovation that was not previously fully appreciated for fish in this time period.

“Sturgeon are considered a ‘primitive’ species, but what we’re showing is that the sturgeon lifestyle is something that’s been selected for in certain conditions and has evolved over and over again,” says Sallan, senior author on the work.

“Fish are very good at finding solutions to ecological problems,” says Stack, first author on the study, who worked on the research as a Penn undergraduate and is now a graduate student at Michigan State University. “This shows the degree of both innovation and convergence that’s possible in fishes. Once their numbers got up large enough, they started producing brand new morphologies that we now see have evolved numerous times through the history of fishes, under similar ecological conditions. ”

The first fossil of Tanyrhinichthys was found in 1984 in a fossil-rich area called the Kinney Brick Quarry, about a half hour east of Albuquerque. The first paleontologist to describe the species was Michael Gottfried, a Michigan State faculty member who now serves as Stack’s advisor for his master’s degree.

“The specimen looks like someone found a fish and just pulled on the front of its skull,” Stack says. Many modern fish species, from the swordfish to the sailfish, have protuberant snouts that extend out in front of them, often aiding in their ability to lunge at prey. But this characteristic is much rarer in ancient fishes. In the 1980s when Gottfried described the initial specimen, he posited that the fish resembled a pike, an ambush predator with a longer snout.

During the last decade, however, several more specimens of Tanyrhinichthys have been found in the same quarry. “Those finds were an impetus for this project, now that we had better information on this enigmatic and strange fish,” Stack says.

At the time that Tanyrhinichthys roamed the waters, Earth’s continents were joined in the massive supercontinent called Pangea, surrounded by a single large ocean. But it was an ice age as well, with ice at both poles. Just before this period, the fossil record showed that ray-finned fishes, which now dominate the oceans, were exploding in diversity. Yet 300 million years ago, “it was like someone hit the pause button,” Sallan says. “There’s an expectation that there would be more diversity, but not much has been found, likely owing to the fact that there just hasn’t been enough work on this time period, especially in the United States, and particularly in the Western United States.”

Aiming to fill in some of these gaps by further characterizing Tanyrhinichthys, Stack, Sallan, and colleagues closely examined the specimens in detail and studied other species that dated to this time period. “This sounds really simple, but it’s obviously difficult in execution,” Stack notes, as fossils are compressed flat when they are preserved. The researchers inferred a three-dimensional anatomy using the forms of modern fishes to guide them.

What they noticed cast doubt on the conception of Tanyrhinichthys as resembling a pike. While a pike has an elongated snout with its jaws at the end of it, allowing it to rush its prey head-on, Tanyrhinichthys has an elongated snout with its jaws at the bottom.

“The whole form of this fish is similar to other bottom dwellers,” Stack says. Sallan also noticed canal-like structures on its snout concentrated in the top of its head, suggestive of the locations where sensory organs would attach. “These would have detected vibrations to allow the fish to consume its prey,” says Sallan.

The researchers noted that many of the species that dwelled in similar environments possessed longer snouts, which Sallan called “like an antenna for your face.”

“This also makes sense because it was an estuary environment,” Sallan says, “with large rivers feeding into it, churning up the water, and making it murky. Rather than using your eyesight, you have to use these other sensory organs to detect prey.”

Despite this, other features of the different ancient fishes’ morphology were so different from Tanyrhinichthys that they do not appear to have shared a lineage with one another, nor do modern sturgeon descend from Tanyrhinichthys. Instead the long snouts appear to be an example of convergent evolution, or many different lineages all arriving at the same innovation to adapt well to their environment.

“Our work, and paleontology in general, shows that the diversity of life forms that are apparent today has roots that extend back into the past,” says Stack.

Reference:
Lauren Sallan, Spencer G Lucas, John-Paul Hodnett, Jack Stack. Tanyrhinichthys mcallisteri, a long-rostrumed Pennsylvanian ray-finned fish (Actinopterygii) and the simultaneous appearance of novel ecomorphologies in Late Palaeozoic fishes. Zoological Journal of the Linnean Society, 2020; DOI: 10.1093/zoolinnean/zlaa044

Note: The above post is reprinted from materials provided by University of Pennsylvania.

Newly unearthed, surprisingly well-preserved conifer fossils from Patagonia, Argentina, show that an endangered and celebrated group of tropical West Pacific trees has roots in the ancient supercontinent that once comprised Australia, Antarctica and South America, according to an international team of researchers.

“The Araucaria genus, which includes the well-known Norfolk Island pine, is unique because it’s so abundant in the fossil record and still living today,” said Gabriella Rossetto-Harris, a doctoral student in geosciences at Penn State and lead author of the study. “Though they can grow up to 180 feet tall, the Norfolk Island pine is also a popular houseplant that you might recognize in a dentist’s office or a restaurant.”

Araucaria grew all around the world starting about 170 million years ago in the Jurassic period. Around the time of the dinosaur extinction 66 million years ago, the conifer became restricted to certain parts of the Southern Hemisphere, said co-author Peter Wilf, professor of geosciences and associate in the Earth and Environmental Systems Institute (EESI).

Today, four major groups of Araucaria exist, and the timing of when and where these living lineages evolved is still debated, Rossetto-Harris said. One grows in South America, and the other three are spread across New Caledonia, New Guinea and Australia, including Norfolk Island. Many are now endangered or vulnerable species. The Norfolk pine group, the most diverse with 16 species, is usually thought to have evolved near its modern range in the West Pacific well after the Gondwanan supercontinent split up starting about 50 million years ago, Rossetto-Harris added.

Researchers from Penn State and the Museo Paleontológico Egidio Feruglio, Chubut, Argentina, found the fossils at two sites in Patagonia — Río Pichileufú, which has a geologic age of about 47.7 million years, and Laguna del Hunco, with a geologic age of about 52.2 million years. They analyzed the fossil characteristics and compared them to modern species to determine to which living group the fossils belonged. Then they developed a phylogenetic tree to show the relationships between the fossil and living species. They reported their findings in a recent issue of the American Journal of Botany.

Unlike the monkey puzzle trees of the living South American group of Araucaria, which have large, sharp leaves, the Patagonian conifer fossils have small, needle-like leaves and cone remains that closely resemble the Australasian Norfolk Island pine group, according to the researchers. They also found a fossil of a pollen cone attached to the end of a branch, which is also characteristic of the group.

“The new discovery of a fossil pollen cone still attached to a branch is rare and spectacular,” said Rossetto-Harris, who is also an EESI Environmental Scholar. “It allows us to create a more complete picture of what the ancestors of these trees were like.”

The researchers used 56 new fossils from Río Pichileufú to expand the taxonomic description of Araucaria pichileufensis, a species first described in 1938 using only a handful of specimens.

“Historically, scientists have lumped together the Araucaria fossils found at Río Pichileufú and Laguna del Hunco as the same species,” Rossetto-Harris said. “The study shows, for the first time, that although both species belong to the Norfolk pine group of Araucaria, there is a difference in conifer species between the two sites.”

The researchers named the new species from Laguna del Hunco Araucaria huncoensis, for the site where it was found. The fossils are about 30 million years older than many estimates for when the Australasian lineage evolved, according to Rossetto-Harris.

The findings suggest that 52 million years ago, before South America completely separated from Antarctica, and during the first few million years after separation was underway, relatives of Norfolk Island pines were part of a rainforest that stretched across Australasia and Antarctica and up into Patagonia, said Rossetto-Harris.

The change in the Araucaria species from the older Laguna del Hunco site to the younger Río Pichileufú site may be a response to the climatic cooling and drying that occurred after South America first became isolated.

“We’re seeing the last bits of these forests before the Drake Passage between Patagonia and Antarctica began to really widen and deepen and set forth a lot of big climatic changes that would eventually cause this version of Araucaria to go extinct in South America, but survive in the Australian rainforest and later spread and thrive in New Caledonia,” Rossetto-Harris said.

The study shows how tiny details can provide the definition needed to reveal big, important stories about the history of life, Wilf added.

The National Science Foundation, National Geographic Society, Botanical Society of America, Geological Society of America, and Penn State provided funding for this project.

Reference:
Gabriella Rossetto‐Harris, Peter Wilf, Ignacio H. Escapa, Ana Andruchow‐Colombo. Eocene Araucaria Sect. Eutacta from Patagonia and floristic turnover during the initial isolation of South America. American Journal of Botany, 2020; 107 (5): 806 DOI: 10.1002/ajb2.1467

Note: The above post is reprinted from materials provided by Penn State.