Rewriting the Mammoth Family Tree

Mammuthus primigenius, Royal British Columbia Museum. From Wikipedia Commons

From Siberia to Alaska, mammoths were widespread in the northern hemisphere during the Last Ice Age and their remains inspired all types of legends. Their lineage arose in Africa during the late Miocene, and first appeared in Europe almost three million years ago. Eventually they dispersed to North America via Beringia, during the Middle Pliocene to Early Pleistocene. Their evolution during the Pleistocene is usually presented as a succession of chronologically overlapping species. M. meridionalis (southern mammoths) arose about 2–1.7 million years ago and was replaced by M. trogontherii (steppe mammoths), which evolved in eastern Asia around 2–1.5 million years ago. Although the relationship among these taxa are uncertain, the prevailing view is that M. columbi (Columbian mammoths) must have arisen from M. trogontheri, which must also be the ancestor of the earliest known examples of M. primigenius (woolly mammoths). A new study by an international team of paleontologists and geneticists offers a glimpse into the origin and evolution of woolly and Columbian mammoth. They used genomic data more than one million years old. So far, the oldest genomic data recovered were from a horse specimen dated to 780–560 thousand years ago.

The researchers recovered genome data from three Early-Middle Pleistocene mammoth molars preserved in Siberian permafrost. The samples were recovered by the late Andrei Sher (Russian Academy of Sciences, Moscow) from the well-documented Olyorian Suite of northeastern Siberia in the 1970s. The first specimen (referred to as ‘Krestovka‘) is morphologically similar to the steppe mammoth (originally defined from the Middle Pleistocene of Europe). It was discovered in 1973 in a cliff exposure along the right side of the Krestovka River. The second specimen (referred to as ‘Adycha’) was recovered in 1976 from a gravel bar in the Adycha River and shows M. trogontherii-like morphology. The third specimen (referred to as ‘Chukochya’) was found in 1971 in a riverbank on the right side of the Bolshaya Chukochya River, and has a morphology consistent with an early form of woolly mammot.

Krestovka specimen showing measurement positions: W = crown width, H = crown height, LL = lamellar length, ET = enamel thickness. From van der Valk et al, 2021

 

Analysis of the DNA suggested that two evolutionary lineages of mammoths inhabited eastern Siberia during the later stages of the Early Pleistocene. One of these lineages is represented by the Krestovka specimen (dated 1.65 Ma), and the second lineage comprises the Adycha specimen (dated 1.3 Ma) along with all Middle and Late Pleistocene woolly mammoths. The results also indicate that the Columbian mammoth is a product of admixture between woolly mammoths and a previously unrecognized ancient mammoth lineage, represented by the Krestovka specimen. This hybridization event took place around 420,000 years ago. The new findings indicate that before the hybridization event North American mammoths belonged to the Krestovka lineage. Previously, a DNA study of the complete mitochondrial genome of Columbian mammoths suggested that interbreeding between late Pleistocene taxa could serve as an indicator of major ecological events, including those surrounding the megafaunal extinctions.

The iconic woolly mammoth evolved into a cold-tolerant, open-habitat specialist through a series of adaptive changes like hair growth, and white and brown fat deposits. The study found that the genes related to these features were present in both the Adycha (87%) and Chukochya (89%) genomes. The findings are suported by the tooth shape of all these northern species that is adapted to grazing   in a cold, open environment.

 

References:

van der Valk, T., Pečnerová, P., Díez-del-Molino, D. et al. Million-year-old DNA sheds light on the genomic history of mammoths. Nature (2021). https://doi.org/10.1038/s41586-021-03224-9

Laura Arppe, Juha A. Karhu, Sergey Vartanyan, Dorothée G. Drucker, Heli Etu-Sihvola, Hervé Bocherens. Thriving or surviving? The isotopic record of the Wrangel Island woolly mammoth population. Quaternary Science Reviews, 2019; 222: 105884 DOI: 10.1016/j.quascirev.2019.105884

Enk, J.; Devault, A.; Widga, C.; Saunders, J.; Szpak, P.; Southon, J.; Rouillard, J. M.; Shapiro, B.; Golding, G. B.; Zazula, G.; Froese, D.; Fisher, D. C.; MacPhee, R. D. E.; Poinar, H. (2016). “Mammuthus population dynamics in Late Pleistocene North America: divergence, phylogeography, and introgression”. Frontiers in Ecology and Evolution. 4. doi:10.3389/fevo.2016.00042.

Enk, J., Devault, A., Debruyne, R. et al. Complete Columbian mammoth mitogenome suggests interbreeding with woolly mammoths. Genome Biol 12, R51 (2011). https://doi.org/10.1186

 

The Middle Eocene Climatic Optimum and the Patagonian floras.

Spore-pollen species from the Eocene of southern South America. From Fernandez et al., 2021

The geological records show that large and rapid global warming events occurred repeatedly during the course of Earth history. Ecological models can predict how biodiversity is affected by those events, but only the fossil record provides empirical evidence about the impact of rising temperatures and atmospheric CO2 on species diversity.

The Middle Eocene Climatic Optimum (MECO, ~40 Ma) was a transient period of global warming that interrupted the general cooling trend initiated at the end of the early Eocene climate optimum (EECO, ~49 Ma). The MECO is related to major oceanographic and climatic changes in the Neo-Tethys and also in other oceanic basins, and lasted about 500–600 Kyr. The MECO altered the pelagic ecosystem with repercussions on the food web structure. The lack of nutrients in the surface waters led to a significant decrease in planktonic foraminiferal accumulation rates, while autotroph nannoplankton accumulation rates remained stable.

Relative frequency of the most common plant groups across the MECO and Late Eocene. From Fernández et al., 2021

The MECO also influenced terrestrial biotas. A new study quantify the response of the floras of southern Patagonia to this warming event. The samples were collected from the Río Turbio Formation in southern Patagonia. The terrestrial palynological assemblage revealed a clear inverse relationship between the abundance of ferns and angiosperms. At the beginning of the MECO, ferns highly increase in abundance (with Cyatheaceae, Dicksoniaceae, and Osmundaceae as the most frequent families), while the abundance of angiosperms decreases dramatically. Podocarpaceae also increases from ~5 % to ~20%. At the core of MECO, ferns drop to a minimum, and angiosperms become dominant. Finally, at the end of the MECO ferns rise again to maximum values and angiosperms decrease.

Palynological analysis also revealed that floras in southern Patagonia were in average ~40% more diverse during the MECO than pre-MECO and post-MECO intervals. The penetration of neotropical migrant species to the highest latitudes along with the persistence of southern Gondwanan natives may have triggered the gradual increasing diversity that can be observed across the MECO.

 

References:

Fernández, D.A., Palazzesi, L., González Estebenet, M.S. et al. Impact of mid Eocene greenhouse warming on America’s southernmost floras. Commun Biol 4, 176 (2021). https://doi.org/10.1038/s42003-021-01701-5

Giorgioni, M., Jovane, L., Rego, E.S. et al. Carbon cycle instability and orbital forcing during the Middle Eocene Climatic Optimum. Sci Rep 9, 9357 (2019). https://doi.org/10.1038/s41598-019-45763-

Sonal Khanolkar, Pratul Kumar Saraswati & Karyne Rogers (2017) Ecology of foraminifera during the middle Eocene climatic optimum in Kutch, India, Geodinamica Acta, 29:2,181-193, DOI: 10.1080/09853111.2017.130084

 

A new giant titanosaur sauropod from the Upper Cretaceous of Argentina

Image credit: Jose Luis Carballido/CTyS-UNLaM/AFP

Since the discovery of dinosaur remains in the Neuquen basin in 1882, Argentina has gained the title of Land of the Giants. The tittle was reinforced by the discoveries of titanosaurs like Argentinosaurus, Dreadnoughtus, Notocolossus, Puertasaurus, and Patagotitan. The study of this diverse group of sauropod dinosaurs embrace an extensive list of important contributions, which started with Richard Lydekker’s pioneering work on Patagonian dinosaurs. 

Titanosauria is a diverse clade of sauropod dinosaurs represented by nearly 80 genera described worldwide. The group includes the smallest (e.g. Rinconsaurus, and Saltasaurus; with estimated body masses of approximately 6 tonnes) and largest sauropods known to date. The Argentinean record of titanosaurs is particularly abundant with almost 50% of the total world record. For years, Argentinosaurus huinculensis was considered the largest dinosaur that ever walked the Earth. The tittle is now in possession of Patagotitan mayorum, discovered in 2010. The first estimations of Patagotitan body mass suggested that it weigh around 70 tons and reached 40 metres (131 feet) long. But a new study published in 2020 indicates that the body mass of Patagotitan ranges between 42–71 tons, with a mean value of 57 tons.

 

Figure 2. Caudal sequence of MOZ-Pv 1221 and detail of caudal vertebrae 3, 4, 11 and posterior element. From Otero et al., 2021

A new specimen from the Candeleros Formation (98 Ma) of Neuquén Province probably exceeds Patagotitan in size. This new giant titanosaur sauropod was discovered in 2012 and is the second taxon from Candeleros Formation, in addition to Andesaurus. The new specimen, identified as MOZ-Pv 1221, includes a sequence of anterior and middle caudal vertebrae, consisting of the first 20 mostly articulated caudal vertebrae and haemal arches plus isolated posterior caudals, pelvis and other appendicular elements. The preserved caudal sequence corresponds to approximately the anterior half of the tail. The neural spines of the anterior caudal vertebrae in MOZ-Pv 1221 are transversely wider than anteroposteriorly long.

Compared to other giant titanosaurs, the recovered appendicular bones of MOZ-Pv 1221 are larger than any known titanosaur described to date. The maximum dorsoventral height at the proximal section of the scapula is 17% higher than in Patagotitan, 26% higher than in Dreadnoughtus, and 130% higher than in Mendozasaurus. The maximum proximo distal length of the pubis of MOZ-Pv 1221 is 166 cm, which is 10% longer than in Patagotitan, 18% longer than in Dreadnoughtus, and 21% longer than in Futalognkosaurus. Although it is not currently possible to estimate the body mass of MOZ-Pv 1221 because of the fragmentary nature of this specimen, it is clear that this new titanosaur partially recovered from the Candeleros Formation can be considered one of the largest titanosaurs that ever walked the Earth.

 

References:

Otero A, Carballido JL, Salgado L, Canudo JI, Garrido AC (2021), Report of a giant titanosaur sauropod from the Upper Cretaceous of Neuquén Province, Argentina, Cretaceous Research https://doi.org/10.1016/j.cretres.2021.104754

Carballido JL, Pol D, Otero A, Cerda IA, Salgado L, Garrido AC, Ramezani J, Cúneo NR, Krause JM. 2017 A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs. Proc. R. Soc. B 284: 20171219.
DOI: 10.1098/rspb.2017.1219

Otero, A., J. L. Carballido, A. Pérez Moreno. 2020. The appendicular osteology of Patagotitan mayorum (Dinosauria, Sauropoda). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2020.1793158

Benson, R. B. J., Campione, N. E., Carrano, M. T., Mannion, P. D., Sullivan, C., Upchurch, P., & Evans, D. C. (2014). Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biology, 12(5), http://doi.org/10.1371/journal.pbio.1001853.

Forgotten women of paleontology: Charlotte Murchison

‘The light of science’, a satirical cartoon by Henry T De la Beche, 1832, depicting Charlotte Murchinson

By the early nineteenth century, the study of the Earth became central to the economic and cultural life of Great Britain. Due to the informal character of the early British geology, women were free to take part in collecting fossils and mineral specimens, and they were allowed to attend lectures, although they were still barred from membership in scientific societies. Early female scientists were often born into influential families, like Mary Lyell, the daughter of the geologist Leonard Horner. Althought Barbara Hastings (1810-1858) and Etheldred Benett (1776–1845) published their works independently, the prevailing pattern was formed by women who have worked in the field but acted as assistants to father, husband, brother, or other male geologist that were no relatives. In these cases, the publication of their findings was not part of accepted females activy, and their contribution is often completely concealed under the name of someone else.

Charlotte Murchison (neé Hugonin) was born on 18 April 1788 in Hampshire, England. When she met her future husband Roderick Murchison, she was a well-educated woman with great interest in science and he was a cavalry officer in the Dragoons who was more interested in horses and dogs than in Geology. The couple married on August 29, 1815. The  first few years of their marriage they travelled extensively in the Continent. In Italy they became friends with Mary Somerville, the “Queen of Nineteenth Century Science.” In her autobiography, Mary Somerville wrote about Charlotte: “Mrs Murchison was an amiable accomplished woman, drew prettily and what was rare at the time she had studied science, especially geology and it was chiefly owing to her example that her husband turned his mind to those pursuits in which he afterwards obtained such distinction.”

Charlotte (née Hugonin), Lady Murchison by Camille Silvy, albumen print, 1860, NPG Ax50535
© National Portrait Gallery, London

In 1824 the couple moved to London where they began to attend lectures on geology and chemistry. A year later, Roderick Murchison read his first paper to the Geological Society. The same year, the couple explored the southern coast of England. In Lyme Regis, they became friends with Mary Anning, and when Mary visited London in July 1829, she stayed with the Murchisons. In a letter to Charlotte Murchison, dated October 11, 1833, Mary writes about the death of her beloved dog Tray which was killed in a landslide: “I would have answered your kind letter by the return of post, if I had been able. Perhaps you will laugh when I say that the death of my old faithful dog quite upset me, the Cliff fell upon him and killed him in a moment before my eyes, and close to my feet, it was but a moment between me and the same fate”.

In 1826, the couple traveled to the coast of Yorkshire. The fossils collected by Charlote were later described by James de Carle Sowerby in the “Mineral Conchology of Great Britain”. In 1827 Sowerby named an ammonite in her honor: Ammonites murchinsoniae. Willian Buckland also used Charlotte’s collection of fossils to illustrate his “Geology and Mineralogy Considered with References to Natural Theology.”

One of Charlotte Murchison’s illustrations for: Murchison, Roderick Impey. The Silurian system (Image: archive.org)

In 1828, Charlotte and her husband joined Charles Lyell on a long journey around Europe. In his notes Charles Lyell praised the active participation of Charlotte: “Mrs . M. is very diligent , sketching, labelling specimens & making out shells in which last she is an invaluable assistant.” Nevertheless, in the summer of 1832, Lyell refused to let women attend his lectures in Geology at Kings College London because he thought that women in a classroom would be “unacademical”. Charlotte and Mary Somerville were among the women who insisted on being allowed to attend the lectures. Some days later, in a letter to his long time friend William Whewell, Mary Somerville wrote: ‘It is decided by the Council of the University that ladies are to be admitted to the whole course, so you can see what in[va]sions we are making on the laws of learned societies, reform is nothing to it”

It was suggested that Lyell’s capitulation was related to Charlotte’s presence among the crowd. In 1834, William Whewell welcomed scientific women to the third meeting of the British Association. In an invitation addressed to Mary Somerville, he wrote: “I expect Mrs. Buckland and Mrs. Murchinson and several other ladies…”

Charlotte continued sketching the cliffs and collecting fossils but due to her health issues, she was not abble to join her husband in many of his late travels. By the 1860s Charlotte’s health has deteriorated. She died on 9 February 1869 at her home in Belgrave Square, London.

 

References:

Kölbl-Ebert, Martina (1997). “Charlotte Murchison (Née Hugonin) 1788-1869”. Earth Sciences History (History of Earth Sciences Society) 16 (1): 39–43 https://doi.org/10.17704/eshi.16.1.97014235w8u4k414

Kölbl-Ebert, M. (2007). The geological travels of Charles Lyell, Charlotte Murchison and Roderick Impey Murchison in France and northern Italy (1828). Geological Society, London, Special Publications, 287(1), 109–117. doi:10.1144/sp287.9

EYLES, V. A. (1971). Roderick Murchison, Geologist and Promoter of Science. Nature, 234(5329), 387–389. doi:10.1038/234387a0

Top fossil discoveries of 2020

Reconstruction of Bagualia alba. Credit: Jorge Gonzalez

2020 started with massive wildfires, locusts devouring crops across East Africa and the coronavirus outbreak. By early March, the World Health Organization (WHO) declared the coronavirus, SARS-CoV-2, to be a pandemic and recommend “surveillance to find, isolate, test and treat every case, to break the chains of transmission.”

The climate crisis escalated. Mega-fires were exacerbated by drought, and anthropogenic climate change. In September, the Arctic sea ice shrank to its second-lowest extent in more than 40 years. Meanwhile fossil explorations were put on hiatus because of the pandemic. We also lost two great paleontologists: Jose Bonaparte and Jenny Clack. But 2020 hasn’t been all bad. Cool new papers about fossil biosignatures, mass extinctions, the tetrapod transition to land (co-authored by Jenny Clack), the evolution of the avian brain, the first well-documented case of bone cancer in a non-avian dinosaur, the nature of the first dinosaur eggs, and perfectly preserved remains of an Ice Age cave bear, shapped a remarkable year in paleontology. Among the most striking fossil discoveries are:

  • Wulong bohaiensis, the dancing dragon

Wulong bohaiensis. From Poust et al., 2020

This small, feathered dromaeosaurid theropod lived in the Early Cretaceous (Aptian) of China, and was discovered by a farmer more than a decade ago. The holotype (D2933) is a complete articulated skeleton (only some ribs are missing) and exhibits special preservation of keratinous structures. Wulong is distinguished by the following autapomorphic features: long jugal process of quadratojugal, cranially inclined pneumatic foramina on the cranial half of dorsal centra, transverse processes of proximal caudals significantly longer than width of centrum, presence of 30 caudal vertebrae producing a proportionally long tail, distally located and large posterior process of the ischium, and large size of supracoracoid fenestra (>15% of total area). The holotype has several gross osteological markers of immaturity like the unfused dorsal and sacral vertebrae, but mature feathers are present across the entire body of Wulong.

  • Tralkasaurus cuyi

Photo: AFP/MUSEO ARGENTINO DE CIENCIAS NATURALES

Tralkasaurus is a medium-sized abelisaurid, much smaller than large abelisaurids as Abelisaurus and Carnotaurus. The name derived from Tralka, thunder in Mapudungun language, and saurus, lizard in Ancient Greek. The specific name “cuyi” derived from the El Cuy, the geographical area at Rio Negro province, Argentina, where the fossil was found. The holotype MPCA-Pv 815 is represented by an incomplete specimen including a right maxilla, distorted and incomplete dorsal, sacral and caudal vertebrae, cervical ribs, and pubis. This four-meter-long (13-foot-long) theropod exhibits a unique combination of traits, including deeply incised and curved neurovascular grooves at the lateral maxillary body that originate at the ventral margin of the antorbital fossa, and shows an extensive antorbital fossa over the maxillary body that is ventrally delimited by a well-marked longitudinal ridge that runs from the promaxillary fenestra level towards the rear of the maxilla.

  • Asteriornis maastrichtensis

Artist’s reconstruction of Asteriornis maastrichtensis. Illustration: Phillip Krzeminski

Asteriornis maastrichtensis is a small member of the clade Pangalloanserae, the group that includes Galliformes and Anseriformes, with an estimated body weight of about 400 grams. The holotype (NHMM, 2013 008) includes a nearly complete, articulated skull with mandibles, and associated postcranial remains preserved in four blocks. It was collected in 2000 by Maarten van Dinther. The new specimen, dated between 66.8 and 66.7 million years ago, reveals a previously undocumented combination of ‘galliform’ and ‘anseriform’ features that emphasizes the modular nature of the skull and bill of crown birds. The narrow and elongate hindlimbs and provenance from nearshore marine sediments suggest that Asteriornis might have had a shorebird-like ecology. The generic name is derived from the name of the Asteria, the Greek goddess of falling stars, and the Greek word ornis for bird. The specific name maastrichtensis honors the provenance of the holotype, the Maastricht Formation (the type locality of the Late Cretaceous Maastrichtian stage).

  • Overoraptor chimentoi

Silhouette of Overoraptor chimentoigen. et sp. nov. (MPCA-Pv805) showing selected skeletal elements. From Motta et al., 2020.

Overoraptor was a gracile theropod that reached about 1.3 m in total length. The name derived from the Spanish word “overo”, meaning piebald, in reference to the coloration of the fossil bones (a pattern of light and dark spots), and the word “raptor” from the Latin for thief. The species name honors Dr. Roberto Nicolás Chimento, who discovered the specimen. The holotype (MPCA-Pv 805) and paratype (MPCA-Pv 818) specimens of O. chimentoi were found in a quarry in association with disarticulated crocodilian and turtle bones. The new taxon comes from the Huincul Formation. The new taxon comes from the Huincul Formation. The unusual combination of a plesiomorphic hindlimb with features that are correlated with cursorial habits, and the more derived forelimb with features that show some adaptations related to active flight, placed Overoraptor, together with Rahonavis in a clade that is sister to Avialae.

  • The Spinosaurus tail

Reconstructed skeleton and caudal series of Spinosaurus aegyptiacus. From Ibrahim et al., 2020.

Spinosaurus aegyptiacus is one of the most famous dinosaur of all time. It was discovered by German paleontologist and aristocrat Ernst Freiherr Stromer von Reichenbach in 1911. Almost a century later, a partial skeleton of a subadult individual of S. aegyptiacus was discovered in the Cretaceous Kem Kem beds of south-eastern Morocco. At the time of deposition, this part of Morocco was located on the southern margin of the Tethys Ocean and it was characterized by an extensive fluvial plain dominated by northward flowing rivers and terminating in broad deltaic systems on Tethys’ southern shores. The neotype of S. aegyptiacus preserves portions of the skull, axial column, pelvic girdle, and limbs. An international team led by Nizar Ibrahim published the first description of the fossil in 2014 and suggested that Spinosaurus may have been specialised to spend a considerable portion of their lives in water.

 

  • Kongonaphon kely.

Reconstruction of Kongonaphon kely. Credit: Alex Boersma

Kongonaphon kely, from the Middle to Late Triassic of Madagascar, is close to the ancestry of dinosaurs and pterosaurs. Discovered in 1998, the holotype (UA 10618) is a partial skeleton composed of a right maxilla, distal portion of the humerus, right femur, proximal portions of the right and left tibia, and indeterminate skeletal fragments. The most striking feature of Kongonaphon is its extraordinarily small size (estimated height,∼10 cm).

 

  • Niebla antiqua

Digital reconstruction of the braincase of Niebla antiqua in right lateral (A), dorsal (B), and posterior (C) views. From Aranciaga et al., 2020

Niebla antiqua, a new specimen from the Late Cretaceous of Río Negro province, is an important addition to the knowledge of abelisaurid diversity. This new taxon is much smaller than other abelisaurids like Carnotaurus and Abelisaurus, with only 4–4.5 metres (13–15 ft) long. It was found near Matadero Hill, located within the Arriagada Farm, at 70 km south from General Roca city, Río Negro province, Argentina. The braincase of Niebla is exquisitely preserved, allowing the recognition of most cranial nerves and vascular foramina.

  • Oksoko avarsan

The skull of Oksoko avarsan in lateral view. From Funston et al., 2020.

Oksoko avarsan is a small oviraptorosaur, with a large, toothless beak and only two fingers on each forearm. The generic name is derived from the word Oksoko, one of the names of the triple-headed eagle in Altaic mythology. The specific name is derived from the Mongolian word avarsan, meaning rescued, because the holotype was rescued from poachers and smugglers in 2006. Preserved in an assemblage of four individuals, the holotype, MPC-D 102/110.a, is a nearly complete juvenile skeleton missing only the distal half of the tail. The excellent preservation of this assemblage provides strong evidence of gregarious behaviour.

 

  • Bagualia alba

Bagualia alba. From Pol et al., 2020

Bagualia alba, recovered from the base of the Cañadón Asfalto Formation, lived 179 million years ago and is the oldest known eusauropod. Discovered in 2007 by an international team of researchers led by Argentinean paleontologist Diego Pol, the holotype of Bagualia alba (MPEF PV 3301) consists of a posterior half of a skull found in articulation with seven cervical vertebrae. It was found in close association with multiple cranial and postcranial remains belonging to at least three individuals. Body mass estimated suggests that Bagualia weighted 10 tons, approximately the size of two African elephants. The teeth have a D-shaped cross section, apical denticles, and buccal and lingual grooves. But the most striking feature of Bagualia is the enamel layer which is extremely thick, seven times that of other pre-volcanic herbivores, and is heavily wrinkled on its outer surface.

  • The origin of Pterosaurs

A partial skeleton of Lagerpeton (Image Credit: Virginia Tech/Sterling Nesbitt)

Lagerpetids are small to medium-sized (less than 1 m long), cursorial, non-volant reptiles from Middle–Upper Triassic of Argentina, Brazil, Madagascar, and North America. Based on the anatomical information from Lagerpeton chanarensis (from the Chañares formation, Argentina), Ixalerpeton polesinensis (from the Santa Maria Formation, Brazil), Kongonaphon kely (from Morondava Basin, Madagascar), and Dromomeron spp. (from North America), an international team lead by Martin Ezcurra from the Museo Argentino de Ciencias Naturales in Buenos Aires, Argentina, elucidated their relationship to pterosaurs. The recognition of this group as the sister taxon to pterosaurs provides clues to study the origin of Pterosauria, its specialized body plan and flying abilities.

References:

Poust, AW; Gao, C; Varricchio, DJ; Wu, J; Zhang, F (2020). “A new microraptorine theropod from the Jehol Biota and growth in early dromaeosaurids”. The Anatomical Record. American Association for Anatomy. doi:10.1002/ar.24343

Ibrahim, N., Maganuco, S., Dal Sasso, C. et al. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature (2020). https://doi.org/10.1038/s41586-020-2190-3

Aranciaga Rolando, M., Cerroni, M. A., Garcia Marsà, J. A., Agnolín, F. l., Motta, M. J., Rozadilla, S., Brisson Eglí, Federico., Novas, F. E. (2020). A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina. Journal of South American Earth Sciences, 102915. doi:10.1016/j.jsames.2020.102915

Gregory F. Funston; Tsogtbaatar Chinzorig; Khishigjav Tsogtbaatar; Yoshitsugu Kobayashi; Corwin Sullivan; Philip J. Currie (2020). «A new two-fingered dinosaur sheds light on the radiation of Oviraptorosauria». Royal Society Open Science, doi:10.1098/rsos.201184

Pol D., Ramezani J., Gomez K., Carballido J. L., Carabajal A. Paulina, Rauhut O. W. M., Escapa I. H. and Cúneo N. R., (2020) Extinction of herbivorous dinosaurs linked to Early Jurassic global warming eventProc. R. Soc. B.28720202310 http://doi.org/10.1098/rspb.2020.2310

 

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

The fossil history of the Christmas tree

Queen Victoria, Prince Albert, and their family around a Christmas tree. From the Illustrated London News (1848)

The Christmas tree is one of the most iconic tradition of modern culture. But long before the advent of Christiany, Egyptians, Celts and Vikings used evergreen plants and trees to celebrate the winter solstice. During Saturnalia, held between 17 and 25 December, Romans also decorated their homes and temples with evergreen boughs. In the 16th century, Germans started the Christmas tree tradition as we now know it. They carried the custom to Britain, though it wasn’t until 1846 that the fir tree became a worldwide custom, after Queen Victoria and her husband, Prince Albert, were sketched in the Illustrated London News standing with their children around a Christmas tree. 

Conifers are cone-bearing seed plants that originated in the Northern Hemisphere during the Middle Pennsylvanian, approximately 310 million years ago. During the LateTriassic and Early Jurassic, the group experienced a considerable diversification that resulted in the divergence of several modern families. Conifers range from small wiry shrubs to giant trees: Sequoiadendron giganteum reachs almost 100 m high, while Microcachrys tetragona from Tasmania has about few centimeters high. The group declined in diversity and abundance after the rise of angiosperms, and many taxa now have very restricted geographic distributions. Conifers also have the longest living non-clonal terrestrial organisms on Earth, with some examples of Pinus longaeva exceeding 4,600 years of age.

Pityostrobus pluriresinosa. From Smith et al., 2016.

Modern Christmas trees belong to a family called Pinaceae, the most species-rich clade of living conifers. The other conifer families include Cupressaceae, Araucariaceae, Podocarpaceae, Cephalotaxaceae, Taxaceae and most recently, the monotypic family Sciadopityacea. Numerous fossils, which include a number of anatomically preserved ovulate cones with many systematically informative characters, documeted the evolutionary history of Pinaceae.

Leaves and ovulate cones are widely variable and help to highlight the Cretaceous radiation of the family. Preserved fossil pinaceous ovulate cones include Pseudoaraucaria, Pityostrobus, Obirastrobus and Eathiestrobus. The estimated age for the initial crown split in Pinaceae between abietoids and pinoids is in the Early Jurassic, ~188 mya. Recent phylogenetic analyses suggest that the earliest- known member of the Pinaceae, Eathiestrobus mackenziei may be more closely related to Pinus than to other extant lineages; while various species of the widespread Cretaceous form genus Pityostrobus are stem members of both extant abietoids and pinoids.

 

 

References:

Leslie, A. B., Beaulieu, J., Holman, G., Campbell, C. S., Mei, W., Raubeson, L. R., & Mathews, S. (2018). An overview of extant conifer evolution from the perspective of the fossil record. American Journal of Botany. doi:10.1002/ajb2.1143 
 
Smith, S. Y., Stockey, R. A., Rothwell, G. W., & Little, S. A. (2016). A new species of Pityostrobus (Pinaceae) from the Cretaceous of California: moving towards understanding the Cretaceous radiation of Pinaceae. Journal of Systematic Palaeontology, 15(1), 69–81. doi:10.1080/14772019.2016.1143885 
 

On the origin of Pterosaurs

The recently discovered and selected bones characterizing the lagerpetid body plan. From Ezcurra et al., 2020

In 1784, Cosimo Alessandro Collini, a former secretary of Voltaire and curator of the natural history cabinet of Karl Theodor, Elector of Palatinate and Bavaria, published the first scientific description of a pterosaur. The specimen came from one of the main sources of such fossils, the Late Jurassic lithographic limestones of northern Bavaria, and Collini, after much deliberation, interpreted it as the skeleton of an unknown marine creature. In 1801, on the basis of Collini’s description, George Cuvier identified the mysterious animal as a flying reptile. He later coined the name “Ptero-Dactyle”. This discovery marked the beginning of pterosaur research.

Holotype specimen of Pterodactylus antiquus,

Pterodactylus antiquus, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA (From Wikipedia Commons)

Pterosaurs were the first flying vertebrates. Their reign extended to every continent and achieved high levels of morphologic and taxonomic diversity during the Mesozoic, with more than 200 species recognized so far. During their 149 million year history, the evolution of pterosaurs resulted in a variety of eco-morphological adaptations, as evidenced by differences in skull shape, dentition, neck length, tail length and wing span. 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. They have been hypothesized to be the close relatives of a wide variety of reptilian clades. Now, a new study published in Nature indicates that lagerpetids are the sister group of pterosaurs.

A partial skeleton of Lagerpeton (Image Credit: Virginia Tech/Sterling Nesbitt)

Lagerpetids are small to medium-sized (less than 1 m long), cursorial, non-volant reptiles from Middle–Upper Triassic of Argentina, Brazil, Madagascar, and North America. Previous studies of lagerpetid anatomy was mostly limited to vertebrae, hindlimbs and a few cranial bones, but new fossil discoveries over the past few years have greatly increased the understanding of this group. Based on the anatomical information from Lagerpeton chanarensis (from the Chañares formation, Argentina), Ixalerpeton polesinensis (from the Santa Maria Formation, Brazil), Kongonaphon kely (from Morondava Basin, Madagascar), and Dromomeron spp. (from North America), an international team lead by Martin Ezcurra from the Museo Argentino de Ciencias Naturales in Buenos Aires, Argentina, elucidated their relationship to pterosaurs. The recognition of this group as the sister taxon to pterosaurs provides clues to study the origin of Pterosauria, its specialized body plan and flying abilities.

Time-calibrated reduced strict consensus tree focused on Pterosauria and Lagerpetidae. From Ezcurra et al., 2020.

The team found at least 33 skeletal traits suggesting an evolutionary link between lagerpetids and pterosaurs. The anterior region of the lagerpetid dentary is ventrally curved similar to those of the early pterosaurs like Austriadactylus. Lagerpetids and pterosaurs also share a unique inner ear morphology among archosaurs, characterized by taller than anteroposteriorly long semicircular canals. The semicircular canals detect head movements and a larger radius increases the sense of equilibrium. The cranial endocasts of D. gregorii and Ixalerpeton reveal strongly developed cerebellar floccular lobes, which resemble the even more developed floccular lobes of pterosaurs. The flocculus plays a key a role in coordinate eye movements, and tends to be enlarged in taxa that rely on quick movements of the head and the body. This condition in Pterosaurs has been hypothesized to be important for information processing related to flight.

Lagerpetids and pterosaurs also share similarities in hand, leg, ankle and pelvic bones. For example pelvic girdles of Lagerpeton and Ixalerpeton have a long pubo-ischiadic contact that extends ventrally up to the level of the anterovental margin of the pubis, as is the case in several early pterosaurs.

 

References:

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

Introducing Bagualia alba, the oldest known eusauropod.

Bagualia alba. From Pol et al., 2020

During the Early Jurassic the southwestern margin of Gondwana was affected by a voluminous magmatic episod related to the emplacement of t heKaroo-Ferrar-Chon Aike Large Igneous Provinces (LIPs). That pulse of volcanism led to global warming, with at least four times the present level of atmospheric CO2, and ocean acidification that resulted in a mass extinction of marine invertebrates and turnover among groups of marine plankton. The period is also characterized by a floristic turnover and the diversification of the conifers, especially modern families, with small coriaceous leaves. Biostratigraphic and high-precision geochronologic results indicate that a major faunal turnover of the sauropodomorph dinosaurs took place in the Early Jurassic, which led to the rise of the eusauropods. Cañadón Asfalto Basin (part of the Chon Aike Igneous Province of Patagonia) in the Chubut Province of Argentina preserves an extraordinary record of Jurassic fauna and flora that marks key events in the evolution of Mesozoic life. The recently described Bagualia alba, recovered from the base of the Cañadón Asfalto Formation, lived 179 million years ago and is the oldest known eusauropod. The name of the new specimen refers to Cañadón Bagual, the site where the fossil was found, and alba (dawn, in Spanish), for its early age.

Reconstruction of Bagualia alba. Credit: Jorge Gonzalez

Discovered in 2007 by an international team of researchers led by Argentinean paleontologist Diego Pol, the holotype of Bagualia alba (MPEF PV 3301) consists of a posterior half of a skull found in articulation with seven cervical vertebrae. It was found in close association with multiple cranial and postcranial remains belonging to at least three individuals. Body mass estimated suggests that Bagualia weighted 10 tons, approximately the size of two African elephants. Among the characters that distinguish Bagualia from other early sauropods area pointed process on the anteroventral end of the premaxilla and anterodorsal end of the dentary; orbital margin of the frontal with a close V-shape pointed medially that results in a short contribution to the orbit; supratemporal fenestra about as anteroposteriorly long as lateromedially wide; and strongly marked proatlantal facets on the laterodorsal margin of the foramen magnum. The teeth have a D-shaped cross section, apical denticles, and buccal and lingual grooves. But the most striking feature of Bagualia is the enamel layer which is extremely thick, seven times that of other pre-volcanic herbivores, and is heavily wrinkled on its outer surface.

In Patagonia, prior to the Toarcian palaeoenvironmental crisis the plant assemblage consisted of sphenophytes, dipteridacean ferns, conifers, seed ferns, Bennetitales and cycads. This diversity is indicative of more humid conditions. By contrast, the less diverse palynologycal assemblage postdating the volcanic event is indicative of seasonally dry and warm conditions, and are largely dominated by the conifers Araucariaceae, Cheirolepidiaceae and Cupressaceae. These large conifers with coriaceous leaves as the dominant trees likely acted as a strongly selective regime favouring the survival and success of eusauropods, which had powerful jaws and an oversized gut. Conversely, the disappearance of many elements of the diverse pre-Toarcian flora could have influenced the extinction of the diverse lineages of smaller non-sauropods, which lacked adaptations to high-fibre herbivory as their gracile skulls and mandibles were less mechanically efficient and their teeth were small, with thin enamel (less than 200 μm) and lacked tooth–tooth occlusion.

 

 

References:

Pol D., Ramezani J., Gomez K., Carballido J. L., Carabajal A. Paulina, Rauhut O. W. M., Escapa I. H. and Cúneo N. R., (2020) Extinction of herbivorous dinosaurs linked to Early Jurassic global warming eventProc. R. Soc. B.28720202310 http://doi.org/10.1098/rspb.2020.2310
 
Cúneo, R., Ramezani, J., Scasso, R., Pol, D., Escapa, I., Zavattieri, A. M., & Bowring, S. A. (2013). High-precision U–Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic. Gondwana Research, 24(3-4), 1267–1275. doi:10.1016/j.gr.2013.01.010 

The endocranial anatomy of Buriolestes

The skull of Buriolestes shultzi. From Müller et al., 2018

The Santa Maria Formation in southern Brazil, comprises a succession of Middle to Late Triassic sedimentary rocks that have been long renowned for their rich tetrapod fossils including one of the oldest (and the best preserved) associations of dinosaur and dinosaur precursor. Buriolestes shultzi, discovered in 2009 and described in 2016, is one of the earliest member of Sauropodomorpha, the group known for giant quadrupedal and herbivorous forms.

Buriolestes lived in what’s now Brazil about 230 million years ago. The holotype (ULBRA-PVT280) includes a partial skull, few pre-sacral, three sacral, and 42 tail vertebrae, left scapula and forelimb lacking most of the manus, paired iliaand ischia, partial left pubis, and nearly complete left hind limb. More remains of Buriolestes were discovered between 2015 and 2018. One of thoses new specimens (CAPPA/UFSM 0035) is a nearly complete and articulated skeleton. More important, the skull is almost entirely preserved, including both lower jaws.

Bones of the skull roof of CAPPA/UFSM 0035. Frontals in (a) dorsal and (b) ventral views. Parietals in (c) dorsal and (d) ventral views. From Müller et al., 2020

The estimated body mass for this new specimen was 4.50 kg. The endocast of Buriolestes exhibits an elongated olfactory tract, differing from the short tract observed in later forms, combined to a relatively small pituitary gland. The CT scans show a well‐developed flocculus of the cerebellum, with this structure projecting into the space between the semicircular canal. The flocculus plays a key a role in coordinate eye movements, and tends to be enlarged in taxa that rely on quick movements of the head and the body. This condition is also observed in another of the earliest sauropodomorphs, Saturnalia. Additionally, the dentary traits are compatible with a faunivorous diet suggesting that early members of the Sauropodomorpha were likely predators.

 

References:

Müller, Rodrigo T.; Ferreira, José D.; Pretto, Flávio A.; Bronzati, Mario; Kerber, Leonardo (2020). “The endocranial anatomy of Buriolestes schultzi (Dinosauria: Saurischia) and the early evolution of brain tissues in sauropodomorph dinosaurs”. Journal of Anatomy. doi:10.1111/joa.13350

Müller, Rodrigo T.; Langer, Max C.; Bronzati, Mario; Pacheco, Cristian P.; Cabreira, Sérgio F.; Dias-Da-Silva, Sérgio (2018). “Early evolution of sauropodomorphs: anatomy and phylogenetic relationships of a remarkably well-preserved dinosaur from the Upper Triassic of southern Brazil”. Zoological Journal of the Linnean Society. 184 (4): 1187–1248. doi:10.1093/zoolinnean/zly009

Cabreira et al., A Unique Late Triassic Dinosauromorph Assemblage Reveals Dinosaur Ancestral Anatomy and Diet, Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.040

Halloween special VIII: The Great Dying

“Out of the Aeons” is a short story by H. P. Lovecraft and Hazel Heald. The story introduces the powerful Ghatanothoa, a Great Old One and the first-born of Cthulhu, brought to Earth from the planet Yuggoth by the Mi-go, an anciente alien race, who built a colossal fortress atop the Mount Yaddith-Gho, and sealed Ghatanothoa inside the mountain. Those who worship this entity hold the god responsible for earthquaques and other natural disasters. Like Groth himself, Ghatanothoa is the harbinger of death.

The fossil record indicates that more than 95% of all species that ever lived are now extinct. Occasionally, extinction events reach a global scale with many species of all ecological types dying out in a near geological instant. These mass extinctions were originally identified in the marine fossil record and have been interpreted as a result of catastrophic events or major environmental changes that occurred too rapidly for organisms to adapt.

Global paleogeographic map for the Permian-Triassic transition showing the location of the Siberian Traps Large Igneous Province. From Vajda et al., 2019

During the last 540 million years five mass extinction events shaped the history of the Earth. The end-Permian extinction (PTB) is the most severe biotic crisis in the fossil record, with as much as 95% of the marine animal species and a similarly high proportion of terrestrial plants and animals going extinct . This great crisis occurred 252 million years ago (Ma), and is linked to the emplacement of the large igneous province of the Siberian Traps. A new study published early this month in the journal Nature Geoscience is the first to conclusively reconstruct the entire cascade of events that lead to the PTB mass extinction.

The team lead by Hana Jurikova used the boron isotope of well preserved shells of brachiopods and paired with carbon and oxygen isotope data, generating a new record of ocean pH for the Permian/Triassic boundary. These findings indicate that the PTB mass extinction was triggered by a multimillennial-scale voluminous injection of carbon to the atmosphere by the emplacement of Siberian Traps sill intrusions. Massive volcanic eruptions with lava flows, released large quantities of sulphur dioxide, carbon dioxide, thermogenic methane and large amounts of HF, HCl, halocarbons and toxic aromatics and heavy metals into the atmosphere. The CO2 greenhouse effect resulted in strong heating and acidification of the surface ocean, which prompted the initial disappearance of all reef-building taxa. Acid rain likely had an impact on freshwater ecosystems and may have triggered forest dieback. 

 

References:

Hana Jurikova et al, Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations, Nature Geoscience (2020). DOI: 10.1038/s41561-020-00646-4

V. Vajda et al. (2020), End-Permian (252Mya) deforestation, wildfires and flooding—An ancient biotic crisis with lessons for the present, Earth and Planetary Science Letters 529 (2020) 115875 https://doi.org/10.1016/j.epsl.2019.115875

H. P. Lovecraft & Hazel Heald, “Out of the Aeons”, Weird Tales magazine, 1935