Pterosaurs and the origin of feathers

Reconstructed T. imperator skeleton, National Museum of Brazil. From Wikimedia Commons

Feathers were once considered to be unique avialan structures linked to birds evolutionary success. Primitive theropods, such as Sinosauropteryx and the tyrannosaurs Dilong and Yutyrannus, and some plant-eating ornithischian dinosaurs, such as Tianyulong, and Kulindadromeus are known from their spectacularly preserved fossils covered in simple, hair-like filaments called ‘protofeathers’. Other integumentary filaments, termed pycnofibres, has been reported in several pterosaur specimens. The discovery of integumentary structures in other pterosaurs, such as Pterorhynchus wellnhoferi (a rhamphorhynchoid pterosaur), and other exquisitely preserved specimens from China, suggest that all Avemetatarsalia (the wide clade that includes dinosaurs, pterosaurs and close relatives) were ancestrally feathered.

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 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.

Details of the cranial crest of MCT.R.1884 and the scanning electron microscope images of melanosomes (g-i). Scale bars, 50 mm (a); 5 mm (b); 2 mm (c); 250 μm (d–f); 2 μm (g–i). From Cincotta et al., 2022.

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.

Melanosomes are granules of the pigment melanin. The diverse shape of the melanosomes recovered from the skin fibres in the crest, monofilaments and branched feathers resembles that in the skin of extant birds and mammals. This is an indication that pterosaurs had the genetic machinery to control the colors of their feathers.

References:

Cincotta, A., Nicolaï, M., Campos, H.B.N. et al. Pterosaur melanosomes support signalling functions for early feathers. Nature (2022). https://doi.org/10.1038/s41586-022-04622-3

Reimagining Amargasaurus

Amargasaurus cazaui. MACN

Dicraeosauridae is a family of mid-sized sauropod dinosaurs characterized by a distinctive vertebral column with paired, long, neural spines. Argentinian dicraeosarids include Amargasaurus cazaui, Pilmatueia faundezi and Bajadasaurus pronuspinax. The group was first described in 1914 by Werner Janensch with the discovery of the nearly complete skeletons of Dicraeosaurus in the expeditions to the upper Jurassic beds of Tendaguru, Tanzania. The discovery of Amargasaurus cazaui in 1991, from the Early Cretaceous beds of La Amarga Formation of Northern Patagonia, renewed the discussion on the peculiar vertebral anatomy of these sauropod dinosaurs.

The hyperelongated hemispinous processes of dicraeosarids were interpreted by some authors as a support structure for a thermoregulatory sail, a padded crest as a display and/or clattering structure, a dorsal hump, or as internal cores of dorsal horn. A new study lead by Ignacio Cerda tested these hypotheses using internal microanatomy and bone microstructure from the holotype of Amargasaurus, and a fragmentary dicreaosaurid specimen (MOZ-Pv 6126-1, consisting of an almost complete anterior dorsal vertebra) also from the La Amarga Formation (Barremian–Aptian, Lower Cretaceous).

Skeletal silhouette of Amargasaurus cazaui. From Cerda et al., 2022.

Despite that the organic components of mineralised tissues decay after death, the inorganic components of bone preserve the spatial orientation of organic components such as osteocyte lacunae, vascular canals, and collagen fibres. Armand de Ricqlès, in the 1960s and 1970s, observed that paleohistological features could be correlated with growth rates and thus could indirectly shed light on the thermal physiology of extinct organisms. Previous paleohistological studies in dicraeosarids revealed particular histological features regarding the vascularization pattern and cortical resorption. 

Bone histology of hyperelongate hemispinous processes of Amargasaurus cazaui. From Cerda et al., 2022

The hemispinous processes from Amargasaurus and MOZ-Pv 6126-1 essentially consist of compact bone tissue. The study lead by Ignacio Cerda also found that secondary remodelling is profuse not only in the perimedullary region but also in the outer cortex. The histological features analized comprise a highly vascularized fibrolamellar bone interrupted with CGMs (cyclical growth marks), presence of obliquely oriented Sharpey’s fibres, and abundant secondary osteons irregularly distributed within the cortex. 

The spatial distribution and orientation of the Sharpey’s fibres indicate the presence of an important system of interspinous ligaments, covered by the integumentary system, which resulted in the formation of a prominent cervical sail in this taxon. However, there is not anatomical or histological evidence that support the presence of a keratinized sheath. The new study also suggests that the cervical sail in Amargasaurus could be used as a display device, a term that includes ‘intraspecific agonistic, deterrent, or sexual display structures’. Unfortunately, the dicraeosaurid record is still too scarce to determine the existence of sexual dimorphism in this clade.

 

References:

Ignacio A. Cerda, Fernando E. Novas, José Luis Carballido, Leonardo Salgado (2022): Osteohistology of the hyperelongate hemispinous processes of Amargasaurus cazaui (Dinosauria: Sauropoda): Implications for soft tissue reconstruction and functional significance. In: Journal of Anatomy. DOI: 10.1111/joa.13659

Windholz, G. J., & Cerda, I. A. (2021). Paleohistology of two dicraeosaurid dinosaurs (Sauropoda; Diplodocoidea) from La Amarga Formation (Barremian–Aptian, Lower Cretaceous), Neuquén Basin, Argentina: Paleobiological implications. Cretaceous Research, 128, 104965. doi: 10.1016/j.cretres.2021.1049

Salgado, L. & Bonaparte, J. F. Un nuevo saurópodo Dicraeosauridae, Amargasaurus cazaui gen et sp. nov., de la Formación La Amarga, Neocomiano de la provincia del Neuquén, Argentina. Ameghiniana 28, 333–346 (1991).

Windholz, G. J., Baiano, M. A., Bellardini, F., & Garrido, A. (2020). New Dicraeosauridae (Sauropoda, Diplodocoidea) remains from the La Amarga Formation (Barremian–Aptian, Lower Cretaceous), Neuquén Basin, Patagonia, Argentina. Cretaceous Research, 104629. doi: 10.1016/j.cretres.2020.10462

 

Top fossil discoveries of 2021

Australotitan cooperensis. Image credit: Eromanga Natural History Museum, Artist: Vlad Konstantinov.

The pandemic is not over yet. Despite the fast development of effective vaccines against COVID-19, the virus continued to spread and mutate throughout the last year, with Omicron taking central stage in the last two months. Much of the blame is the unequal distribution of vaccines, a phenomeno described by Tedros Adhanom Ghebreyesus as a “catastrophic moral failure”.

But 2021 was not all bad. Cool new papers about ancient DNA, a billion-year-old freshwater protist, mass extinctions, the abundance of Tyrannosaurus rex, the description of two new spinosaurids from the Wessex Formation of the Isle of Wight, the speed of theropods, and the flower revolution, shapped a remarkable year in paleontology. Among the most striking fossil discoveries are:

  • MOZ-Pv 1221, a new giant titanosaur sauropod from the Upper Cretaceous of Argentina.

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

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.

  • Ninjatitan zapatai, the earliest known titanosaur.

Anterior caudal vertebra of Ninjatitan zapatai. From Gallina et al., 2021

Ninjatitan lived 140 million years ago and reached 20 meters in length (65 feet). The firs remains were discovered in 2014 by technician Jonatan Aroca. The holotype (MMCh-Pv228) includes an incomplete anterior–middle dorsal vertebra, a middle dorsal centrum, and anterior caudal centra with the base of neural arches preserved, a complete left scapula, a fragmentary distal femur, and a nearly complete left fibula of a single individual. The generic name honors the Argentine paleontologist Sebastián “Ninja” Apesteguía. The species name refers to Mr. Rogelio “Mupi” Zapata, in recognition for his work as a technician of the Museo Municipal Ernesto Bachman. Despite the fragmentary nature of the new taxon, three derived characters of Ninjatitan support its possition within the clade Titanosauria: 1) presence of procoelous anterior caudal centra; 2) pneumatized neural arch of anterior caudal vertebrae; and 3) position of the acromial process near the glenoid level. The position of Ninjatitan, as a basal titanosaur, extends the origin of this clade by at least 10 Myr.

  • Taytalura alcoberi, the father of lizards.

Taytalura alcoberi.Image credit: Jorge Blanco

The holotype (PVSJ 698), dated to be around 231 million years old, was discovered by a team lead by Ricardo Martínez in 2001 in the Ischigualasto Formation. The tiny skull reached only two centimeters in size, but it was well-preserved. Micro-CT scanning of the skull reveals some features shared with sphenodontians, including a tetraradiate squamosal, differing from the triradiate condition of squamates; a medially curved mandibular symphysis, as in early sphenodontians; and a small coronoid. Taytalura is about 11 million years younger than the oldest known lepidosaurs from Europe, and approximately the same age as the first known crown lepidosaurs in South America. The new finding provides strong evidence that stem lepidosaurs were contemporaneous with the first assemblages of crown lepidosaurs.

  • Australotitan cooperensis, the southern titan.

3-D digital restorations of the holotype (EMF102) of the titanosaurian Australotitan cooperensis (From Hocknull et al. 2021).

The Winton Formation, located in the uppemost unit of the Eromanga Basin, provides an important source of information about the Cretaceous of Australia. In the last two decades, four new dinosaurs were recovered in this area, including Australotitan cooperensis, the largest dinosaur ever found in Australia. The holotype (EMF102), discovered in 2005, comprises a partial left scapula, partial left humerus, complete right humerus, right ulna, both pubic bones and ischia, and partial right and left femora. Three aditional specimens were referred to the genus: EMF164, EMF105, and EMF165. The fragmented femur of specimen EMF164 has a length of 2.146 metres (7.04 feet), similar in size to the femora of Futalognkosaurus and Dreadnoughtus.

  • Ypupiara lopai, the first unenlagiine dromaeosaurid species from Brazil.

Right maxilla of DGM 921-R with details of teeth. Scale bar: 10 mm. From Brum et al., 2021.

Ypupiara lopai from the Maastrichtian of the Bauru Group is the first unenlagiine dromaeosaurid species from Brazil. The holotype (DGM 921-R) includes a partial preantorbital portion of a right maxillary, with three teeth in loci, and a partial posterior portion of a right dentary. The generic name means ‘the one who lives in the water’, an allusion to a Tupian myth about an aquatic creature. The specific name honors Alberto Lopa, the holotype’s discoverer. Ypupiara was found between the 40s and 60s in Peirópolis, near Uberaba, and placed in storage at the National Museum of Brazil. Unfortunately, the fossil was lost when the museum was consumed by a fire on 2 September 2018, but photographs of the specimen survived.

  • Mussaurus and the social behaviour of early sauropodomorphs.

Nest with eggs of Mussaurus patagonicus. Image credit: Credit: Diego Pol.

The discovery of 80 individuals of Mussaurus patagonicus, ranging from embryos to fully-grown adults, and more than 100 eggs, provides the earliest evidence of complex social behaviour. The eggs and nests of Mussaurus were found in three distinct horizons in the middle of the Laguna Colorada Formation. X-ray computed tomography reveals that the eggs were arranged in two or three layers within elongate depressions or trenches that appear to have been purposely excavated. The research team lead by Diego Pol calculated the site’s age at 193 million years, predating previous records of social behavior in dinosaurs by at least 40 My. The researchers also suggest that sociality may have influenced the early success and the first global radiation of sauropods.

  • Stegouros elengassen, an armoured dinosaur from Chile.

Skeletal anatomy of the S. elengassen holotype. From Soto-Acuña et al., 2021.

Stegouros elengassen, a new specimen from the Late Cretaceous Dorotea Formation of southern Chile, offers new evidence that contributes to the understanding of the relationships among the ankylosaurs from Gondwana. The holotype (CPAP–3165) was discovered in 2017 at the lower section of the Dorotea Formation. Stegouros lived about 72 to 75 million years ago, and reached 2 meters in lenght (six feet). The generic name is derived from the the Greek word “stego” (roof ) and the Greek word “uros” (tail) in reference to the covered tail. The specific name “elengassen” comes from an armoured beast in the mythology of the Aónik’enk people.

  • ‘Baby Yingliang’

The new specimen ‘Baby Yingliang’. Credit: Lida Xing

The new specimen (YLSNHM01266), nicknamed Baby Yingliang, is preserved curled inside its egg, with the head positioned ventral to the body. The oviraptorid affinity of Baby Yingliang is supported by several characers, including the crenulated ventral margin of premaxilla; the edentulous skull; the U-shaped mandibular symphysis; and the highly arched dentary. The vertebral column is estimated to have 22 presacral vertebrae. The pubis points posteroventrally, similar to that of modern birds, althought it is unclear how much of its orientation is genuine. The almost complete skeleton is ∼23.5 cm in total length. It was found in Shahe Industrial Park in Ganzhou City and acquired by the director of Yingliang Group, Mr Liang Liu. It was stored in Yingliang Stone Nature History Museum until the museum staff discovered it.

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

Pablo Ariel Gallina, Juan Ignacio Canale, & José Luis Carballido (2021).The earliest known titanosaur sauropod dinosaur. Ameghiniana58(1), 35–51 http://dx.doi.org/10.5710/AMGH.20.08.2020.3376

Martínez, R.N., Simões, T.R., Sobral, G. et al. A Triassic stem lepidosaur illuminates the origin of lizard-like reptiles. Nature 597, 235–238 (2021). https://doi.org/10.1038/s41586-021-03834-3

Hocknull SA, Wilkinson M, Lawrence RA, Konstantinov V, Mackenzie S, Mackenzie R. 2021. A new giant sauropod, Australotitan cooperensis gen. et sp. nov., from the mid-Cretaceous of Australia. PeerJ 9:e11317 https://doi.org/10.7717/peerj.11317

Brum, Arthur Souza, Pêgas, Rodrigo Vargas, Bandeira, Kamila Luisa Nogueira, Souza, Lucy Gomes de, Campos, Diogenes de Almeida, & Kellner, Alexander Wilhelm Armin. (2021). A new Unenlagiinae (Theropoda: Dromaeosauridae) from the Late Cretaceous of Brazil. https://doi.org/10.1002/spp2.1375

Pol, D., Mancuso, A.C., Smith, R.M.H. et al. Earliest evidence of herd-living and age segregation amongst dinosaurs. Sci Rep 11, 20023 (2021). https://doi.org/10.1038/s41598-021-99176-1

Soto-Acuña, S., Vargas, A.O., Kaluza, J. et al. Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile. Nature (2021). https://doi.org/10.1038/s41586-021-04147-1

Waisum Ma et al. (2021). An exquisitely preserved in-ovo theropod dinosaur embryo sheds light on avian-like prehatching postures, iScience  DOI: https://doi.org/10.1016/j.isci.2021.103516

 

The Flower Revolution

The rise of angiosperms was accompanied by massive expansion in biodiversity. From Benton et al., 2021

Angiosperms, or flowering plants, represent almost 90% of all living land plants. The group first appeared in the fossil record during the Early Cretaceous and by the Late Cretaceous, angiosperms came to dominate plant diversity. Charles Darwin’s fascination and frustration with the evolutionary events associated with the origin and early radiation of angiosperms are legendary. On 22 July 1879, in a letter to Joseph Dalton Hooker, Darwin refers to the early evolution of flowering plants as an “abominable mystery”. Since Darwin many new fossils have been found and facilitated the calibration of molecular clock age estimates for various angiosperm clades. Before the Aptian, the only convincing angiosperm megafossils are from the Barremian Las Hoyas flora of Spain and the Yixian flora of northeastern China. By contrast, there is an extensive pre-Aptian pollen record of angiosperms.

Model of the ancestral flower (From Sauquet et al., 2017)

The Angiosperm Terrestrial Revolution (Benton et al., 2021) reshaped the entire terrestrial ecosystem. Flowering plants altered climate and water cycles, and drove a massive expansion in biodiversity of numerous key groups of fungi, insects, arachnids, reptiles, mammals and birds. But angiosperm success lies no only in their possesion of flowers. They have smaller genomes on average than other plants, which lead to small cell sizes in angiosperms with tightly-packed internal structures. Other key innovations like high vein density and densely packed stomata are also related to genome size. Stomata are the controlled pores through which plants exchange gases with their environments, and play a key role in regulating the balance between photosynthetic productivity and water loss through transpiration

Atmospheric CO2 concentrations and paleotemperatures were the major drivers of floristic turnover. Multiple climate proxy records, identified the EECO as the warmest interval of the past 65 million years. During EECO (Eocene Climate Optimum), the warmest interval of the past 65 million years, emerged many angiosperm dominated forest. Today, many organisms depend substantially or entirely on angiosperms for their existence, especially in tropical rain forests. Among them are about 15 000 species of lizards, birds and mammals. 

References:

Benton, Michael J., et al. 2021. The Angiosperm Terrestrial Revolution and the Origins of Modern Biodiversity. New Phytologist. Wiley Online Library https://doi.org/10.1111/nph.17822

Sauquet, H., von Balthazar, M., Magallón, S. et al. The ancestral flower of angiosperms and its early diversification. Nat Commun 8, 16047 (2017). https://doi.org/10.1038/ncomms16047

Halloween special VI: Baron Nopcsa and the dinosaurs of Transylvania

The Nopcsa Sacel Castle

Transylvania is mostly known for its myths about vampires. Following the publication of Emily Gerard’s The Land Beyond the Forest (1888), Jules Verne published Le Château des Carpathes (The Castle of the Carpathians) in which Transylvania is described as one of the most superstitious countries of Europe. But of course, the most significant contribution to the development of the Transylvania place myth was Bram Stoker’s Dracula, published in 1897.

Sacel Castle, at the heart of the Hateg region, is the last residence of the Nopcsa family, known as one of the strangest in Transylvania. Among the members of the family, there were governmental counselors and chancellors of the Transylvanian Court, members of the Royal Minister and of the Royal House, and knights of imperial orders. Baron Franz Nopcsa of Felsöszilvás (1877-1933), was one of the most prominent researchers and scholars of his day, and is considered the forgotten father of dinosaur paleobiology.

Baron Nopcsa in Albanian Uniform, 1915

In 1897 Nopcsa became a student of Vienna University and by the age of 22, he presented the first description and paleobiological analysis of one of the Transylvanian dinosaurs before the Vienna Academy of Science: Telmatosaurus transsylvanicus. The holotype, BMNH B.3386, was found in the Haţeg Basin.

The Hateg region, situated at the heart of Transylvania, is the cradle of Romanian civilization, but 70 million years ago it was a tropical island in the Thetys Ocean, noted for the occurrence of aberrant, endemic, and dwarfed fauna. In 1914, Nopcsa theorized that the “limited resources” found on islands have an effect of “reducing the size of animals” over the generations. Nopcsa noted several palaeobiological features in support of his views, including what he perceived as the common presence of pathological individuals, and considered this condition a reasonable result of the ecologically impoverished and stressed environment inhabited by this fauna. The recognition of ameloblastoma in a Telmatosaurus dentary discovered from the same area represents the best documented case of pathological modification identified in Transylvanian dinosaurs.

Doda, left, and Nopcsa, circa 1931. They spent nearly 30 years together. (Hungarian Natural History Museum)

Nopcsa continued to do collecting in the Haţeg Basin, at least until the beginning of the First World War. Among the fossils that Nopcsa studied were the duck-billed Telmatosaurus transylvanicus, the bipedal and beaked Zalmoxes robustus, the armored Struthiosaurus transylvanicus, and the sauropod Magyarosaurus dacus. In addition, he made extensive travels across much of Europe to visit palaeontological museums and to meet fellow scientists. In his field trips Nopcsa was now accompanied by Elmas Doda Bajazid, whom Nopcsa met in Albania and convinced to become his secretary. The men spent nearly 30 years togheter.

On 25 April 1933, Nopcsa’s body and that of his secretary Bajazid were found at their Singerstrasse residence. Nopcsa left a letter to the police: ”The motive for my suicide is a nervous breakdown. The reason that I shot my longtime friend and secretary, Mr Bayazid Elmas Doda, in his sleep without his suspecting at all is that I did not wish to leave him behind sick, in misery and without a penny, because he would have suffered too much. I wish to be cremated.”

 

References:

David B. Weishampel & Oliver Kerscher (2012): Franz Baron Nopcsa, Historical Biology: An International Journal of Paleobiology, DOI:10.1080/08912963.2012.689745

CSIKI, Z. & BENTON, M.J. (2010): An island of dwarfs – Reconstructing the Late Cretaceous Haþeg palaeoecosystem. Palaeogeography, Palaeoclimatology, Palaeoecology 293: 265 – 270 doi:10.1016/j.palaeo.2010.05.032

Dumbravă, M. D. et al. A dinosaurian facial deformity and the first occurrence of ameloblastoma in the fossil record. Sci. Rep. 6, 29271; doi: 10.1038/srep29271 (2016).

 

 

The American incognitum and the History of Extinction Studies

 

Georges Cuvier (1769 -1832) and the painting of Charles Wilson Peale’s reconstruction of the American incognitum

Extinction is the ultimate fate of all species. More than 95% of all species that ever lived are now extinct. But prior to the 18th century, the idea that species could become extinct was not accepted. However, as the new science of paleontology began bringing its first major discoveries to light, researchers began to wonder if the large vertebrate fossils of strange creatures unearthed by the Enlightenment explorers were indeed the remains of extinct species.

In 1739, French soldiers under the command of Baron Charles le Moyne de Lougueuil recovered a tusk, femur, and three curious molar teeth from Big Bone Lick, Kentucky, a place known in several American Indian narratives. Lougueuil sent these specimens to the Cabinet du Roi (Royal Cabinet of Curiosities) in Paris. In 1762, Louis Jean-Marie Daubenton, a zoologist at the Jardin du Roi concluded that the femur and tusk from the Longueuil’s collection were those of a large elephant, the “Siberian Mammoth,” but the three molars came from a gigantic hippopotamus.

Molar collected at Big Bone Lick in 1739 and described in Paris in 1756. (Georges Cuvier, Recherches sur les ossemens fossiles)

By the early 18 century it was inconceivable for many researchers that a species could be vanished. Naturalist Georges-Louis Leclerc de Buffon, wrote in 1749 about the extinction of marine invertebrates, but he adopted Daubenton’s view that the Siberian mammoth and the animal of the Ohio, known as the American incognitum, were both northern forms of the extant elephant rather than a vanished species. British anatomist William Hunter was the first to speculate that these remains might be from an extinct species. In 1799, the discovery of an American incognitum femur from Quaternary deposits in the Hudson River Valley led to excavations organized by Charles Wilson Peale. In 1801, the excavations resulted in the recovery of an almost complete skeleton. Peale reconstructed the skeleton with help from the American anatomist Caspar Wistar, and the displayed the mounted skeleton in public in December of that year.

In 1806 Georges Cuvier resolved the controversy about the  American incognitum demonstrating that both the Siberian mammoth and the “animal de l’Ohio” were elephants, but of different species. He described the Ohio elephant as a mastodon and he reached the conclusion that probably represented an extinct species. Cuvier was also the first to suggested that periodic “revolutions” or catastrophes had befallen the Earth and wiped out a number of species. But, under the influence of Lyell’s uniformitarianism, Cuvier’s ideas were rejected as “poor science”. The modern study of mass extinction did not begin until the middle of the twentieth century. One of the most popular of that time was “Revolutions in the history of life” written by Norman Newell in 1967.

 

References:

Macleod, N. The geological extinction record: History, data, biases, and testing. Geol. Soc. Am. Spec. Pap. 505, (2014), DOI: 10.1130/2014.2505(01)​

Marshall, Charles R., Five palaeobiological laws needed to understand the evolution of the living biota, Nature Ecology & Evolution 1, 0165 (2017), DOI: 10.1038/s41559-017-0165 .

A Brief Introduction to Conservation Paleobiology

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Over the past 50 years, the pace and magnitude of human-induced global changes has accelerated dramatically. The term defaunation was created to designate the declining of top predators and herbivores triggered by human activity, that results in a lack of agents that control the components of the ecosystems vegetation. Although anthropogenic climate change is playing a growing role, the primary drivers of modern extinctions seem to be habitat loss, human predation, and introduced species. The same drivers that contributed to ancient megafaunal and island extinctions.

The emerging discipline of conservation paleobiology is supplying necessary information to understand how ecosystems vary naturally through time and space and how they respond to major perturbations. The fossils that have provided such data include phytoplankton, zooplankton, fossil pollen, seeds, leaves, wood, invertebrate animals with hard parts, and vertebrate animals. They are particularly useful because they often show high fidelity to the living communities. Quaternary fossils have proven especially informative for addressing conservation questions, but useful information has also come from much older fossil deposits, reaching back millions of years.

1024px-bison_near_a_hot_spring_in_yellowstone

Bison near a hot spring in Yellowstone National Park (From Wikimedia Commons).

The analytical methods that allow comparing present with past fall into two main categories: taxon-based and taxon-free. Taxon-based methods rely on the presence, absence, or abundances of certain taxa and their underlying diversity. Taxon-free methods use metrics that reflect ecosystem function rather than structure. Depending on the availability of fossils and the type of conservation question being asked, one or the other approach may be more appropriate.

Taxon-based paleontological data are critical in deciding if a “natural” landscape represents a historical or a novel ecosystem. Historical ecosystems are those that still have at least 70% of the habitats that were present 500 years ago and that contain fewer than 5 people/km2. In the world’s first national park, Yellowstone National Park, USA, paleontological data influenced critical management decisions by demonstrating that Yellowstone preserves a historical ecosystem. Fossil deposits verified that almost all of the mammal species that had occupied the region for millennia are still present. Also, palynological records show that the current vegetation has persisted with only minor fluctuations in abundance of dominant taxa for at least 8000 years.

Lyuba, the best preserved mammoth mummy in the world, at the Field Museum of Natural History (From Wikimedia Commons).

Lyuba, the best preserved mammoth mummy in the world, at the Field Museum of Natural History (From Wikimedia Commons).

Taxon-free paleontological can often be related to environmental parameters with statistical significance data, and are critical for understanding whether certain ecosystems are approaching “tipping points,” as demonstrated by analysis of diatoms, pollen, and sediments from lake cores.

Fossils have also figured prominently  with efforts to reconstruct copies of species that humans have driven to extinction either recently (passenger pigeons) or in the deeper past (mammoths). Unfortunately, the ecosystems that supported many extinct species no longer exist, so survival outside of captivity would be difficult. In addition, preventing the extinction of extant species and habitats numbering in the thousands already is challenging, so the prospects of sustaining “de-extincted” species are poor at best. Media reports are presenting de-extinction in an optimistic framework, and conveying the impression that we face a real possibility of bringing mammoth back from extinction in  the near future. Of course, this is far from truth. We will never be able to recreate most extinct species in their purest form. Ultimately,  genetic engineering to simulate extinct life also raises ethical and legal concerns.

 

References:

Anthony D. Barnosky et al. Merging paleobiology with conservation biology to guide the future of terrestrial ecosystems. Science, 2017 DOI: 10.1126/science.aah4787

Rodolfo Dirzo et al., Defaunation in the Anthropocene, Science 345, 401 (2014); DOI: 10.1126/science.1251817

Braje, T.J., Erlandson, J.M., Human acceleration of animal and plant extinctions: A Late Pleistocene, Holocene, and Anthropocene continuum. Anthropocene (2013), http://dx.doi.org/10.1016/j.ancene.2013.08.003

Richmond, D.J., Sinding, M-H.S., Gilbert, M.T.P. (2016). The potential and pitfalls of de-extinction. — Zoologica Scripta, 45, 2236DOI: 10.1111/zsc.12212