Top fossil discoveries of 2022

Meraxes gigas. Image credit: J. Gonzalez

It was the season of Light, it was the season of Darkness. The year began with the War between Russia and Ukraine, and the subsequent humanitarian crissis. Global fuel and food prices soared because of the conflict. Mega-fires were exacerbated by drought, and anthropogenic climate change. The State of the Cryosphere Report 2022 indicates that complete loss of Arctic sea ice in summer is now inevitable, which, combined with heat waves in Antarctica will lead to the irreversible sea-level rise. Meanwhile, the International Union for Conservation of Nature (IUCN) added 66 new species to its Red List.

But 2022 was not all bad. Cool new papers about the oldest animal, an Edmontosaurus “mummy”, the rise of dinosaurs and climate change, world’s oldest heart, world’s oldest brain, world’s oldest DNA,  and a graveyard, shapped a remarkable year in paleontology. Among the most striking fossil discoveries are:

Dearc sgiathanach.

Postcranial skeleton and dentition of Dearc sgiathanach. From Jagielska et al., 2022

Discovered in 2017 by Amelia Penny, the holotype (NMS G.2021.6.1-4), a well preserved, articulated, skeleton, was found at Rubha nam Brathairean (Brothers’ Point), Isle of Skye, in north-west Scotland, in the Lonfearn Member of the Lealt Shale Formation (Bathonian, Middle Jurassic). The specimen is almost complete with the exception of the anterior and dorsal portions of the cranium, the end of the tail, hindlimbs elements, and parts of the wings. The name comes from the Scottish Gaelic language and has a double meaning: “winged reptile” and “reptile from Skye.” Phylogenetic analysys places Dearc sgiathanach within the clade Angustinaripterini. The new specimen suggests that many “pterodactyloid” features convergently evolved in other groups, and hightlights that the Middle Jurassic was a time of increasing diversification in pterosaur history.

First Triassic records of pterosaurs in the southern hemisphere

Pachagnathus and Yelaphomte. Image credit: Jorge Blanco

The description of two new specimens from Quebrada del Barro Formation in north-western Argentina are the first unequivocal Triassic records of pterosaurs in the southern hemisphere. Previous to this new work, the only record of a Triassic pterosaur in southern hemisphere was Faxinalipterus minima, from the Caturrita Formation in southern Brazil, although now is considered as a basal Ornithodira.

Yelaphomte praderioi was a small pterosaur. The holotype (PVSJ:914) is represented by a partial rostrum with the anterior part of both maxillae and palatine, and the posterior portion of both premaxillae. Pachagnathus benitoi was a moderate-sized pterosaur. The holotype (PVSJ:1080) is a partial mandibular symphysis lacking anterior end, preserving one tooth and three alveoli from the the left side, and the roots of three teeth and two alveoli from the right side.

Pterosaurs and the origin of feathers

Scanning electron micrographs of melanosomes in the soft tissues of MCT.R.1884

A new specimen of an adult Tupandactylus imperator, a tapejarid pterosaur from north-eastern Brazil, preserves extensive soft tissues which provides more evidence that pterosaurs had feathers. The new specimen (MCT.R.1884) comprises the posterior portion of the cranium and the remains of a soft tissue cranial crest preserved on five separate slabs. Two types of fibrous integumentary structures were present. The monofilaments (approximately 30 mm long and 60–90 μm wide) resemble those present in the anurognathid Jeholopterus ningchengensis and the ornithischian dinosaur Tianyulong. The most striking feature is the presence of fossil melanosomes with diverse morphologies that supports the hypothesis that the branched integumentary structures in pterosaurs are feathers. The fossil, originally poached from an undetermined outcrop of the Early Cretaceous Crato Formation, was in privated hands for an unknown period of time and later deposited at the Royal Belgian Institute of Natural Sciences (RBINS). The fossil was repatriated to Brazil early this year. 

Abditosaurus kuehnei.

Fossil elements of Abditosaurus kuehnei collected during the 2012-2014 excavations. Image credit: Rubén Contreras. From Vila et al., 2022.

Abditosaurus kuehnei from the Late Cretaceous of Catalonia is the most complete titanosaur skeleton discovered in Europe so far. The specimen reached 17,5 meters in length (57 ft) with a body mass of 14,000 kg. The holotype, an associated, semi-articulated, partial skeleton, includes several isolated teeth, 12 cervical vertebrae, 7 dorsal vertebrae, 3 chevrons, scapular and pelvic bones, right tibia, parts of the femurs and a complete humerus. Phylogenetic analyses indicates that Abditosaurus is a saltasaurid lithostrotian titanosaur. Saltasaurinae, a clade from South America and Africa, includes Neuquensaurus, Saltasaurus and Paralititan. The arrival of Abditosaurus to Europe via a dispersal event from Africa ocurred after a regressive event during the Early Maastrichtian (70.6 Ma) that affected the central Tethyan margin and northern Africa.

Maip macrothorax

Maip macrothorax. Image credit: Agustín Ozán

Maip macrothorax is a large-bodied megaraptorid from lower Maastrichtian Chorrillo Formation in Santa Cruz Province, Argentina. The holotype (MPM 21,545) includes the axis (only lacking both prezygapophyses and its right postzygapophysis), several dorsal and caudal vertebrae, three incomplete cervical ribs, numerous incomplete or fragmentary dorsal ribs, numerous gastral elements, left coracoid, distal end of a second metatarsal, and fragments of the scapula. The generic name, Maip, is derived from an evil entity in Aonikenk mythology that represents “the shadow of the death”. The specific name, macro, derives from the Greek word makrós (meaning long), and the Latin word thorax (meaning chest) in reference to its wide thoracic cavity (which has, approximately, more than 1.20 m width). The specimen was discovered in 2019, but due the outbreak of the COVID-19 pandemic in early 2020 the dig was temporarily interrupted.

Meraxes gigas

Reconstruction of the skeleton of Meraxes. From Canale et al., 2022

Meraxes gigas, a new specimen from the Upper Cretaceous of northern Patagonia, Argentina, is the most complete carcharodontosaurid ever found and provides new information about the skull length in Giganotosaurus. The holotype (MMCh-PV 65) is represented by a nearly complete skull without mandibles, pectoral and pelvic girdles, fore- and hindlimbs, fragments of cervical and dorsal vertebrae, complete sacrum, and proximal and middle caudal vertebral series. The first remains were discovered in 2012 in the Upper Cretaceous Huincul Formation of northern Patagonia, Argentina. The new specimen weighed more than 4 tons and measured up to 11 meters (36 feet) long. Histological analysis indicates that this dinosaur was an adult of 45-53 years of age at death. The skull of Meraxes is profusely ornamented and has a total length of 127 cm. This is the most complete cranium of any Carcharodontosaurinae. Applying scaling equations and measurements taken from Meraxes, the team lead by Dr. Juan Canale from the Museo Paleontológico Ernesto Bachmann, has estimated the size of the Giganotosaurus skull. The results indicate a length of 163 cm, one of the biggest theropod skulls ever found.

Jakapil kaniukura


Jakapil kaniukura. Image credit: Pepe Mateos/Agencia Telam

Jakapil kaniukura is the first definitive thyreophoran species from Argentina. The first remains were found in 2014, in the upper beds of the Candeleros Formation at the ‘Rinconada de la Piedra Blanca’ in Rio Negro Province, Argentina. The genus name Jakapil (Ja-Kapïl: shield bearer), comes from the ‘gananah iahish’, Puelchean or northern Tehuelchean language. The specific epithet, comprising kaniu (crest) and kura (stone), comes from the Mapudungun language and refers to the diagnostic ventral crest of the mandible. The holotype (MPCA-PV-630), with an estimated living mass of 4-7kg (9-15lb), is a partial skeleton of a subadult individual that includes fragmentary cranial bones, a nearly complete left lower jaw, partial vertebral elements, a complete dorsal rib, a partial coracoid, a nearly complete left scapula, a partial right scapula, two partial humeri, a possible partial right ulna, and more than forty osteoderms.

Elemgasem nubilus

Elemgasem nubilus. Image credit: Abel Germán Montes

Elemgasem nubilus, from the Portezuelo Formation of Argentina, is the first abelisaurid from the Turonian–Coniacian interval. The new specimen increases the diversity of this clade at a time of significant turnover in the tetrapod fauna of South America, marked by global climate change, and mass extinction events recorded worldwide in the marine realm. The holotype (MCF-PVPH-380), discovered in 2002, includes several axial and appendicular elements. Elemgasem measured about 4 meters (13 feet) long. The genus name refers to the Tehuelche god Elemgasem, the ‘owner’ of the animals and founder of the northern Tehuelche people. The specific name nubilus comes from the Latin ‘foggy days’ in reference to the climatic conditions during the palaeontological expedition when this specimen was discovered.

Natovenator polydontus

Natovenator polydontus. Image credit: Yusik Choi

Natovenator polydontus, a new theropod dinosaur from the Upper Cretaceous of Mongolia, was a small swimmer. The holotype (MPC-D 102/114) is a mostly articulated skeleton with a nearly complete skull, with anatomical characteristics very similar to the aquatic adaptations in Halszkaraptor. The most striking feature is the configuration of its articulated dorsal ribs that indicates that Natovenator had a dorsoventrally flattened and streamlined body, similar to penguins. The generic name is derived from the Latin nato (swim) and venator (hunter), in reference to to the hypothesized swimming behaviour and diet of the new taxon. Thespecific name polydontus, from the Greek polys (many) and odous (tooth) refers to the presence of the unusually number of teeth of the new specimen.

Patagopelta cristata

Patagopelta

Digitized reconstruction of Patagopelta. Image credit: CONICET

Patagopelta cristata, a new nodosaurid ankylosaur from the Allen Formation (Campanian–Maastrichtian), Rio Negro Province, Argentina, is the first species of ankylosaurus described for Argentina. The new specimen also offers new evidence that contributes to the understanding of the relationships among the ankylosaurs from Gondwana. The new specimen lived about 70 million years ago. The body length estimated is ∼2 meters (comparable in size with the nodosaurid Struthiosaurus from the Late Cretaceous of Europe). The generic name is derived from the word ‘Patago’ (referring to the Argentinian Patagonia) and ‘pelta’ (shield in Greek), in reference to the presence of a large number of osteoderms covering the dorsal surface of the body. The specific name ‘cristata‘ (crest in Latin) refers to the presence of crests on the anterior surface of the femur and the lateral osteoderm of the cervical rings.

 

References:

Martínez, R.N., Andres, B., Apaldetti, C. and Cerda, I.A. (2022), The dawn of the flying reptiles: first Triassic record in the southern hemisphere. Pap Palaeontol, 8: e1424.https://doi.org/10.1002/spp2.1424

Canale, J.I. et al., New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction. Current Biology (2022). doi:10.1016/j.cub.2022.05.057

Aranciaga Rolando, A.M., Motta, M.J., Agnolín, F.L. et al. A large Megaraptoridae (Theropoda: Coelurosauria) from Upper Cretaceous (Maastrichtian) of Patagonia, Argentina. Sci Rep 12, 6318 (2022). https://doi.org/10.1038/s41598-022-09272-z

Lee, S., Lee, YN., Currie, P.J. et al. A non-avian dinosaur with a streamlined body exhibits potential adaptations for swimming. Commun Biol 5, 1185 (2022). https://doi.org/10.1038/s42003-022-04119-9

 

 

Christmas edition: Foraminiferal Christmas cards

Christmas greetings slide 1912, by Arthur Earland. Image credit: © The Natural History Museum, London

During the early decades of the 20th-century, Arthur Earland and Edward Heron-Allen were volunteers at the Natural History Museum. They both studied Foraminifera, a group of single celled protozoa with shells of different composition and granuloreticulose pseudopodia. The first record of the group is from the Early Cambrian (540 million years ago) and extend to the present day. Their size range is from about 100 micrometers to almost 20 centimeters long. Their importance as tool for paleoclimate reconstruction was recognized early in the history of oceanography.

Each Christmas, Earland and Heron-Allen exchanged unusual but beautiful Christmas cards made with foraminifera. The most popular of these Christmas-themed slide is from 1912 and has Earland’s initials (“AE”), the word “Xmas”, and the year. This lovely tradition ended when their partnership dissolved, possibly because Heron-Allen alone was elected a Fellow of the Royal Society for his Foraminifera work in 1919.

Portraits of Heron-Allen and A. Earland. Image credit: © The Natural History Museum, London

Arthur Earland was a Civil servant and employed in the Post Office Savings Bank Department. He was born at Lewisham on November 3, 1866. In the late 1880 he joined the Quekett Microscopical Club, and by 1891 he had published his first paper. He was one of the several researchers that worked with the material collected by the HSM Challenger.

Edward Heron-Allen was a lawyer and polymath, who translated the works of Omar Khayyam. He was born on 17 December 1861 in London. His interest in science began during his days at Elstree Preparatoy School. In 1894 he published his first paper, entitled ‘Prolegomena towards the Study of the Chalk Foraminifera’, a practical guide to the preparation and study of fossil foraminifera. In 1907, he start working with A. Earland. This association lasted until 1933.

Christmas greetings slide 1921, by Arthur Earland. Image credit: © The Natural History Museum, London

Among the many achievements of ArthurEarland and Edward Heron-Allen are the description of 650 species of Foraminifera from the famous Terra Nova Antarctic expedition.

Edward Heron-Allen died on March 28, 1943, in Sussex, England, shortly after the dead of his wife. The Heron-Allen collection (containing 740 slides of foraminifera) and associated library are held by Natural History Museum. Arthur Earland was elected a Fellow of the Royal Society of Edinburgh in 1942. He died on March 27, 1958.

References:

HEDLEY, R. Mr. Arthur Earland. Nature 181, 1440–1441 (1958). https://doi.org/10.1038/1811440b0

Gregory Richard Arman (1943), Edward Heron-Allen 1861-1943 Obit. Not. Fell. R. Soc.4447–454  https://doi.org/10.1098/rsbm.1943.0015

Introducing Patagopelta cristata

Patagopelta

Digitized reconstruction of Patagopelta. Image credit: CONICET

Ankylosauria is a clade of herbivorous, armored ornithischian dinosaurs subdivided in two major clades: the Ankylosauridae and the Nodosauridae. The most derived members of this group are characterized by shortened skulls, pyramidal squamosal horns, and tail clubs. Fossil evidence of armored dinosaurs from Gondwana is scarce. Patagopelta cristata, a new nodosaurid ankylosaur from the Allen Formation (Campanian–Maastrichtian), Rio Negro Province, Argentina, is the first species of ankylosaurus described for Argentina. The new specimen also offers new evidence that contributes to the understanding of the relationships among the ankylosaurs from Gondwana.

Patagopelta lived about 70 million years ago. The body length estimated is ∼2 meters (comparable in size with the nodosaurid Struthiosaurus from the Late Cretaceous of Europe). The generic name is derived from the word ‘Patago’ (referring to the Argentinian Patagonia) and ‘pelta’ (shield in Greek), in reference to the presence of a large number of osteoderms covering the dorsal surface of the body. The specific name ‘cristata‘ (crest in Latin) refers to the presence of crests on the anterior surface of the femur and the lateral osteoderm of the cervical rings.

Femur of Patagopelta cristata. From Riguetti et al., 2022

Femur of Patagopelta cristata. From Riguetti et al., 2022

The ankylosaur material were collected by different research groups from the 1980s onwards. The holotype (MPCA-SM-78) is represented by a cervical half-ring element. The cranial material is represented by a single isolated tooth. The axial skeleton include a partial cervical neural arch, four dorsal vertebrae, two synsacral fragments and seven caudal vertebrae. The best preserved element is the femur. The femoral head is well developed and hemispherical, and it’s separated from the greater trochanter by a deep fossa. The fourth trochanter is placed proximally on the femoral shaft. The dermal elements include cervical and post-cervical osteoderms.

 Phylogenetic analysis recovered Patagopelta within Nodosaurinae, along with other ‘mid’-Cretaceous nodosaurids from North America. These results support the proposal that South American ankylosaurs may have migrated from North America during the Late Cretaceous. The new study suggests that the small size of Patagopelta is linked to some event of dwarfism as in the case of Struthiosaurus from the Hateg Island.

References:

Facundo Riguetti, Xabier Pereda-Suberbiola, Denis Ponce, Leonardo Salgado, Sebastián Apesteguía, Sebastián Rozadilla & Victoria Arbour (2022) A new small-bodied ankylosaurian dinosaur from the Upper Cretaceous of North Patagonia (Río Negro Province, Argentina), Journal of Systematic Palaeontology, 20:1, 2137441, DOI: 10.1080/14772019.2022.2137441

Forgotten women of paleontology: Joan Wiffen, the dragon lady

 

Joan Wiffen (1922-2009) with the humerus of a plesiosaur, Elasmosaurus keyesi. From Wikimedia Commons

New Zealand is renowned for its mountains, its volcanoes, and beautiful landscapes. This long-isolated island was once part of Gondwana, but between 100 and 80 million years ago, New Zealand broke away from Gondwana and started to move toward its present position, with the accompanying formation of the Tasman Sea. Since then New Zealand has had its own geological history and developed a unique flora and fauna. Almost five decades ago it was thought that New Zealand had escaped the worldwide dominance of dinosaurs, but all that changed in the early 1970s, thanks to the work of a couple of amateur paleontologists: Joan and M.A. Wiffen.

Joan Pederson was born on February 4, 1922, in Mount Eden, Auckland. Her familiy lived in Hawke’s Bay, a rural coastal region on New Zealand’s northernmost island. As a child, she collected sea shells, and stones. Unfortunalety, her father did not believe in education for girls and Joan must left school at the age of 12. During World War II, she  joined the Woman’s Auxiliary Air Force. She was trained as a radar plotter, and later worked as a medical clerk. In September 12, 1953, she married Montague Arthur Wiffen. The couple had two children, Christopher (born 1956) and Judith (born 1961). 

 

Joan Wiffen, from Caldwell, M, 2012

In the late 1960s, Joan took evening classes in geology. Later, she and her husband joined a local rock and mineral club and visited many fossil localities around New Zealand. In 1972, they made their first visit to  Mangahouanga Stream in Hawke’s Bay. Two years later, Joan discovered the bone of an unidentified animal. In 1979, Dr Ralph Molnar confirmed that the bone was the tailbone of a theropod dinosaur, the first ever discovered in New Zealand. 

In 1986, Joan co-authored with Bill Moisley, a major paper about the plesiosaur materials that she and her husband collected over the years.  Her  work on fossil reptiles was recognised by a special award from the Geological Society of New Zealand that same year. Joan Wiffen also found an ankylosaur, a sauropod dinosaur, mosasaurs, and a pterosaur. She was the author and co-author of more than a dozen scientific papers . In her autobiography,  “Valley of the Dragons”, she wrote that an academic advised her to sign as J. Wiffen when writing papers because  ‘men have better chances of publishing than elderly female housewives‘. In 1995 Joan was awarded a CBE (‘Commander of the British Empire’). She died on June 30, 2009.

 

References:

Caldwell, M. (2012). In Memorium : Dr. Joan Wiffen (1922-2009). Bulletin de La Societe Geologique de France, 183(1), 5–6. doi:10.2113/gssgfbull.183.1.5 

Wiffen, Joan (1991). Valley of the Dragons: The Story of New Zealand’s Dinosaur Woman.  Random Century, Auckland.

Halloween Special X: The legend of a Patagonian Monster

Primo Capri and his Plesiosaur. Photo: Rafael Soriani, 1922

On December 10, 1823, Mary Anning discovered the first complete Plesiosaur skeleton at Lyme Regis in Dorset. Noticed about the oddity of the specimen, George Cuvier wrote to William Conybeare suggesting that the find was a fake produced by combining fossil bones from different animals. But despite their unusual body plan Plesiosaurs were a highly successful group of Mesozoic marine reptiles. Their four limbs are enlarged and modified as propulsive flippers, the trunk is short and stiff, and proportional head size seems to vary inversely with neck length.

The idea of surviving plesiosaurs was popularize in the works of Jules Verne and Sir Arthur Conan Doyle. “The Monster of Lake LaMetrie” (1899), a short story by Wardon Allan Curtis, features an encounter between a scientist and a plesiosaur that has been cast up from the hollow center of Earth.  The modern emergence of the Loch Ness monster in the 1930s was deeply influenced by these stories and films like The Lost World (1925) and King Kong (1933).  Even now, the discovery of fossil remains of plesiosaurs from the freshwater fluvial deposits of the mid-Cretaceous Kem Kem Group of Morocco sparked some sensationalist headlines about the Loch Ness Monster. But a decade before the media frenzy around Nessie, there was an argentinian expedition to hunt a living plesiosaur.

Clemente Onelli (courtesy of Archivo General de la Nación, Argentina). From Brinkman and Vizcaíno, 2014

Clemente Onelli (courtesy of Archivo General de la Nación, Argentina). From Brinkman and Vizcaíno, 2014

It all began in January, 1922, when Martin Sheffield, a flamboyant American hunter and gold prospector living in Patagonia, wrote a letter to Buenos Aires Zoo Director, Clemente Onelli. In the letter, Sheffield claimed that he saw a very strange creature in a lake near Esquel, a small Patagonian town in the foothills of the Andes: “I have been able to see, in the middle of the lake, an enormous animal with a head like a swan and enormous size and the movement in the water makes me suppose a crocodile body.

Sheffield’s account and similar reports from Laguna Epuyén led Onelli to think that the mysterious creature could be a plesiosaur. He organized an expedition to capture the beast alive and bring it back to the zoo in Buenos Aires. Onelli also invited Elmer S. Rigg, an associate curator of palaeontology at the Field Museum of Natural History in Chicago. Riggs, like most of the scientific community utterly discredited that a plesiosaurus was still alived. However, some people took it seriously. That was the case of Dr. Albarracin, President of the Society for the Protection of Animals. He demanded that the Minister for the Interior stop the expedition, under the law 2786, which prohibits the hunting of rare animals.

A report from the Plesiosaur expedition. Scientific American 127: 2

Despite the fail of the expedition, the fever around the plesiosaur did not stop. Primo Capraro, a businessman from Bariloche, used a float with the figure of a plesiosaur making it parade through the streets of the town. Rafael D’Agostino (music) and Amílcar Morbidelli (lyrics) wrote a tango about the creature. And one hundred years later the stories around the monster continued. The last reported sighting was on August, 2020.

 

References:

Brinkman, Paul & Vizcaíno, Sergio. (2014). Clemente Onelli’s sketch map and his first-hand, retrospective account of an early fossil-hunting expedition along the Río Santa Cruz, southern Patagonia, 1888–1889. Archives of natural history. 41. 326-337. 10.3366/anh.2014.0251.

MATTERS, L., (1922). An antediluvian monster: Is the Argentine Plesiosaurus a fake or a scientific marvel?? Scientific American 127: 2

The enigmatic Scleromochlus and the origin of pterosaurs.

Life reconstruction of Scleromochlus taylori. Image credit: Gabriel Ugueto

Pterosaurs were the first flying vertebrates, and their reign extended to every continent and achieved high levels of morphologic and taxonomic diversity during the Mesozoic. The oldest-known pterosaurs appear in the fossil record about 219 million years ago. Most Triassic pterosaurs are small but already had a highly specialized body plan linked to their ability to fly: shoulder girdle with strongly posteroventrally enlarged coracoid braced with the sternum and laterally facing glenoid fossa; forelimb with pteroid bone and hypertrophied fourth digit supporting a membranous wing; and pelvic girdle with prepubic bone and strongly developed preacetabular process.

Due to the fragile nature of their skeletons and the absence of fossils with transitional morphologies, the origin of pterosaurs is one of the most elusive questions in vertebrate paleontology. In 2020, a study led by Martin Ezcurra demonstrated a close relationship between Lagerpetidae and Pterosauria, and found Scleromochlus as the earliest-diverging pterosauromorph. The recognition of lagerpetids as the sister taxon to pterosaurs provides clues to study the origin of Pterosauria, its specialized body plan and flying abilities.

The newly anatomical features of Scleromochlus taylori. From Foffa et al., 2020.

Scleromochlus taylori, from the early Late Triassic of Scotland, is a tiny reptile with extremely long hindlimbs known from seven largely articulated skeletons on small slabs. It was discovery in 1907 by Arthur Smith Woodward who identified Scleromochlus as a small bipedal running or leaping dinosaur. As early as 1914, Huene interpreted Scleromochlus as an arboreal climbing and leaping pseudosuchian close to the origin of pterosaurs.  A new study led by Dr Davide Foffa support the hypothesis that the first flying reptiles evolved from small, potentially bipedal, cursorial ancestors.

Using microcomputed tomographic techniques, the team led by Dr Davide Foffa, provides new key information of Scleromochlus anatomy. The skull length of Scleromochlus is ~50% of the presacral vertebral column length, as in early pterosaurs; the maxilla has an anterior process that tapers to a point and has a weakly concave anterior margin; the occipital neck is extremely short; the pubis is less than 50% the length of the femur; the femoral head is ‘hook-shaped‘; and the length of metatarsal V is less than half length of metatarsal III.

 

References:

Foffa, D., Dunne, E.M., Nesbitt, S.J. et al. Scleromochlus and the early evolution of Pterosauromorpha. Nature (2022). https://doi.org/10.1038/s41586-022-05284-x

Ezcurra, M.D., Nesbitt, S.J., Bronzati, M. et al. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4

Bennett SC.  Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopperPeerJ 8:e8418 (2020) https://doi.org/10.7717/peerj.8418

An 80-million-year-old fossilized braincase from an enantiornithine bird

MPM-334-1 is a diminutive basicranium of a skeletally mature enantiornithine bird. From Chiappe et al., 2022.

Birds are extraordinarily intelligent and they can rival mammals in terms of relative brain size and behavioural complexity. The clade originated from a theropod lineage more than 150 million years ago. By the Early Cretaceous, they diversified, evolving into a number of groups of varying anatomy and ecology. Recent studies have shown that corvids and some parrots are capable of cognitive achievement comparable to those of great apes. They manufacture and use tools, solve puzzles, and plan for future needs. Futhermore, they share with humans and a few other animal groups a rare capacity for vocal learning.

Over the last decades, several discovered fossils of theropods and early birds have enriched our knowledge of the evolution of the avian skull. Now, the discovery of an exceptionally well preserved braincase from an Upper Cretaceous (~80 Ma) enantiornithine bonebed in southeastern Brazil shed light on the early evolution of the avian braincase, brain and inner ear.

Enantiornithine braincase MPM-334-1 from the Late Cretaceous of southeastern Brazil; (a) Ventral view, (b) dorsal view. From Chiappe et al., 2022

Enantiornithes are the most diverse group of Mesozoic birds. The clade shows a mosaic of characters, reflecting their intermediate phylogenetic position between the basal-pygostylians and modern bird, and their remains, ranging from the size of hummingbirds to turkeys, have been collected on every continent except Antarctica. MPM-334-1 (Museu de Paleontologia de Marília, São Paulo State) is a diminutive basicranium of a skeletally mature enantiornithine bird. The endocast comprises impressions from the external surfaces of most of the medulla, parts of the cerebellum, and the ventral portion of the optic tectum.

MPM-334-1 displays a mosaic combination of plesiomorphic dinosaurian traits and a set of endocranial transformations: a flexed brain that are remarkably similar to those of extant birds, a ventralized foramen magnum and ‘crown-like’ endosseous labyrinth. The new study lead by Luis Chiappe, suggest a more complex scenario for the evolution of the avian skull and central nervous system than had previously been understood, with key features of the modern avian endocranium evolving much earlier than what was formerly thought. 

 

References:

Chiappe LM, Navalón G,Martinelli AG, Nava W, Field DJ. 2022 Fossil basicranium clarifies the origin of theavian central nervous system and inner ear. Proc. R. Soc. B289: 20221398. https://doi.org/10.1098/rspb.2022.1398

Chiappe, L. M., Ji, S. & Ji, Q. Juvenile birds from the Early Cretaceous of China: implications for enantiornithine ontogeny. Am. Mus. Novit. 3594, 1–46 (2007).

Introducing Elemgasem nubilus

Elemgasem nubilus. Image credit: Abel Germán Montes

Abelisauroidea is the best known carnivorous dinosaur group from Gondwana. The clade was erected by the legendary paleontologist Jose Bonaparte with the description of Abelisaurus Comahuensis. These ceratosaurian theropods are medium to large, robust animals, such as the Carnotaurus and the Majungasaurus of Madagascar. The group exhibits short, round snouts; thickened teeth; short, stocky arms; and highly reduced forearms. 

The Cretaceous beds of Patagonia holds an extraordinary record of abelisaurids, although there is a paucity during the whole Coniacian.  This lack of specimens during this interval is a worldwide phenomenon. Thus, the Late Cretaceous record of abelisaurids is represented by two intervals: the Cenomanian–Turonian, with taxa from Argentina, Africa and Madagascar, and the Santonian–Maastrichtian, with taxa from Argentina, Brazil, Africa, Madagascar and India. Elemgasem nubilus, from the Portezuelo Formation of Argentina, is the first abelisaurid from the Turonian–Coniacian interval. The new specimen increases the diversity of this clade at a time of significant turnover in the tetrapod fauna of South America, marked by global climate change, and mass extinction events recorded worldwide in the marine realm.

Femur histology of Elemgasem nubilus. From Baiano et al., 2022.

The holotype (MCF-PVPH-380), discovered in 2002, includes several axial and appendicular elements, and exhibits the following features: a marked rugosity on the lateral surface of the fibula, a high lateral surface and a high proximolateral wall of the calcaneum, as well as posterior caudal centra with oval articular surfaces and a groove on the ventral surface. Osteohistological analysis of the femur and phalanx III-2 indicates that this new specimen was at least 8 year old and had achieved sexual maturity but was still growing.

Elemgasem measured about 4 meters (13 feet) long. The genus name refers to the Tehuelche god Elemgasem, the ‘owner’ of the animals and founder of the northern Tehuelche people. The specific name nubilus comes from the Latin ‘foggy days’ in reference to the climatic conditions during the palaeontological expedition when this specimen was discovered.

Location map and geological strata from which the specimen Elemgasem nubilus MCF-PVPH-380 holotype was recovered. From Baiano et al., 2022.

In the Late Cretaceous Abelisauridae splits in the clade Majungasaurinae and and the clade Brachyrostra. Post-Coniacian brachyrostrans constitute a natural group, Furileusauria. Phylogenetic analysis recovered Elemgasem as an unstable taxon, occupying all possible positions within Furileusauria, or as a sister taxon of this clade. 

Elemgasem nubilus lived about 90 million years ago in one of the most phylogenetically diverse fauna from the middle Late Cretaceous of South America, which includes crocodiles, pterosaurs, ornithopods, and four distinct lineages of tetanuran theropods, such as Megaraptor, the alvarezsaurid Patagonykus, the dromaeosaurids Neuquenraptor, Pamparaptor and Unenlagia, and an indeterminate neornithine. 

 

 

References:

Mattia A. Baiano, Diego Pol, Flavio Bellardini, Guillermo J. Windholz, Ignacio A. Cerda, Alberto C. Garrido & Rodolfo A. Coria Elemgasem nubilus: a new brachyrostran abelisaurid (Theropoda, Ceratosauria) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina (2022). https://doi.org/10.1002/spp2.1462 

Jakapil kaniukura, the shield bearer

Jakapil kaniukura. Image credit: Pepe Mateos/Agencia Telam

The Late Cretaceous of Argentina is represented by a high diversity and abundance of Theropoda and Sauropoda, while ornithischian remains are scarce and are mainly represented by hadrosaurids. Thyreophora is a clade of ornithischian dinosaurs that includes stegosaurs, ankylosaurs and basal forms as Emausaurus ernsti, Scutellosaurus lawleri, and Scelidosaurus harrisonii. The group is characterized by the presence of a postcranial dermal armour extending from the neck to the tip of the tail. Their fossil record is mainly known from the northern hemisphere, and its presence in the Gondwanan continents remains poorly known with some skeletal remains and tracks in South America, Africa, Madagascar, Australia, New Zealand and Antarctica. Basal thyreophorans could be bipedal or combine bipedal and quadrupedal locomotion, while stegosaurs and ankylosaurs were obligate quadrupeds.

Jakapil kaniukura is the first definitive thyreophoran species from Argentina. The first remains were found in 2014, in the upper beds of the Candeleros Formation at the ‘Rinconada de la Piedra Blanca’ in Rio Negro Province, Argentina. The genus name Jakapil (Ja-Kapïl: shield bearer), comes from the ‘gananah iahish’, Puelchean or northern Tehuelchean language. The specific epithet, comprising kaniu (crest) and kura (stone), comes from the Mapudungun language and refers to the diagnostic ventral crest of the mandible.

 

Holotype of Jakapil kaniukura. From Riguetti et al., 2022.

The holotype (MPCA-PV-630), with an estimated living mass of 4-7kg (9-15lb), is a partial skeleton of a subadult individual that includes fragmentary cranial bones, a nearly complete left lower jaw, partial vertebral elements, a complete dorsal rib, a partial coracoid, a nearly complete left scapula, a partial right scapula, two partial humeri, a possible partial right ulna, and more than forty osteoderms.

The skull of Jakapil is incomplete. The premaxilla, maxilla and mandible reveal a short skull in comparison with most non-ankylosaurid thyreophorans. The mandible resembles that of heterodontosaurids and basal ceratopsians. The basipterygoid processes are not close to the midline. The ventral process is small and carries a foramen. The predentary is pyramidal-shaped with a rounded apex, and two large and rounded lateral processes. The most striking feature is the presence of a ventral crest of the mandible. The axial elements are similar to those of Scelidosaurus. The humeri are strongly reduced in size. The femoral fragments also resemble those of basal ornithischians. Despite the incompleteness of the material, the overall limb dimensions and estimations suggest a bipedal stance in Jakapil.

 

References:

Facundo J. Riguetti, Sebastián Apesteguía & Xabier Pereda-Suberbiola (2022) A new Cretaceous thyreophoran from Patagonia supports a South American lineage of armoured dinosaurs. https://doi.org/10.1038/s41598-022-15535-6

Introducing Meraxes gigas

Meraxes gigas. Image credit: J. Gonzalez

The Cretaceous beds of Patagonia have yielded the most comprehensive record of Cretaceous non-avian theropods from Southern Hemisphere, which includes at least five main theropod lineages: Abelisauroidea, Carcharodontosauridae, Megaraptora, Alvarezsauridae, and Unenlagiidae. These record facilitates the understanding of the origin, evolution, and radiation of theropods from Gondwana. The first remains of dinosaurs were found near Neuquen city by an officer army in 1882 and were sent to Florentino Ameghino, the “founder father” of Argentinian paleontology.

Carcharodontosauridae includes the largest land predators in the early and middle Cretaceous of Gondwana, like the popular, Giganotosaurus carolinii. Members of this theropod family were first recorded in Cenomanian beds of Africa. The group possess widely fenestrated skulls, and in some cases with heavily sculptured facial bones. Another common trait is the fusion of cranial bones. Meraxes gigas, a new specimen from the Upper Cretaceous of northern Patagonia, Argentina, is the most complete carcharodontosaurid ever found and provides new information about the skull length in Giganotosaurus.

Reconstruction of the skeleton of Meraxes. From Canale et al., 2022

The holotype (MMCh-PV 65) is represented by a nearly complete skull without mandibles, pectoral and pelvic girdles, fore- and hindlimbs, fragments of cervical and dorsal vertebrae, complete sacrum, and proximal and middle caudal vertebral series. The first remains were discovered in 2012 in the Upper Cretaceous Huincul Formation of northern Patagonia, Argentina. The new specimen weighed more than 4 tons and measured up to 11 meters (36 feet) long. Histological analysis indicates that this dinosaur was an adult of 45-53 years of age at death.

The name comes from Meraxes, a dragon of the Song of Ice and Fire saga (by George R.R. Martin), with golden eyes and silver scales, named for a god of the Valyrian Freehold. The specific name “gigas” (gigant in Greek) makes reference to the size of the species.

Skull of Meraxes. Image credit: Fundación Azara

The skull of Meraxes is profusely ornamented and has a total length of 127 cm. This is the most complete cranium of any Carcharodontosaurinae. Applying scaling equations and measurements taken from Meraxes, the team lead by Dr. Juan Canale from the Museo Paleontológico Ernesto Bachmann, has estimated the size of the Giganotosaurus skull. The results indicate a length of 163 cm, one of the biggest theropod skulls ever found.

Meraxes also preserves near-complete forelimbs which are about half the length of the femur, a feature comparable to late tyrannosaurids and abelisaurids. This reveals a trend towards forelimb reduction in megapredatory theropod. Quantitative analyses suggest that this evolutionary convergence is especially pronounced between forelimb ratios of Meraxes and the tyrannosauroid Tarbosaurus.

References:

Canale, J.I. et al., New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction. Current Biology (2022). doi:10.1016/j.cub.2022.05.057

Novas, F.E., et al., Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.04.001