Wednesday, 17 June 2015

Hall of Vertebrate Origins

Following on from my previous post about the Hall of Saurischian Dinosaurs at the American Museum of Natural History in New York, which I visited last year, I now present selected photographs of specimens exhibited in the Hall of Vertebrate Origins. The gallery is situated next door to the Saurischian gallery, hence why it is next on this blog. 

All photos taken by Mo Hassan at the American Museum of Natural History, New York, in June 2015.

Tupuxuara leonardii Kellner, 1994
Thalassodromidae; Pterosauria; Sauropsida; Chordata

One of the first specimens to greet you, if you look up, as you enter the Hall of Vertebrate Origins, is a mounted cast of a Brazilian pterosaur called Tupuxuara (named after a Tupi familiar spirit in Native American mythology). Looking at it superficially, it looks like it has a giant head, a little body, spindly legs, and very long arms. With soft tissue in place, this animal probably looked a bit like a giant toucan or some other tropical bird, with membranous skin between the long finger and the hind limbs to serve as wings, and probably a fuzzy body and a colourful head crest.

This specimen is a cast, AMNH 29080, of a specimen collected in Ceará, Brazil, dating from Cenomanian in the mid-Cretaceous. More on pterosaurs will follow in the next post...

Alligator prenasalis (Loomis, 1904)
Alligatoridae; Crocodilia; Sauropsida; Chordata

The genus Alligator contains two living species: the critically endangered Chinese alligator (A. sinensis) from the Yangtze River, and the well-known American alligator (A. mississippiensis) from the southeastern United States. The genus formerly contained many other species which have now become extinct, proving that alligators were found in a far broader range across the globe in former times. This specimen, AMNH 4994, was collected in South Dakota in 1906, and dates from the Oligocene period, around 35 million years ago. This suggests that South Dakota was then warmer and wetter.

Gavialis browni Mook, 1932
Gavialidae; Crocodilia; Sauropsida; Chordata

This long-snouted skull belongs to a relative of today's gharial (Gavialis gangeticus), an endangered fish-eating crocodilian from the Indian subcontinent. This specimen, AMNH 6279, was collected in 1922 from Pakistan, in the Siwalik Hills. These hills are famed for the fossils of early hominids (apes) like Sivapithecus and the okapi-like antlered giraffe Sivatherium, amongst other fossils. It dates to 5 million years ago, and differs very little from the modern gharial.

Voay robustus (Grandidier & Vaillant, 1872)
Crocodylidae; Crocodilia; Sauropsida; Chordata

The smallest modern crocodile species, the dwarf crocodile (Osteolaemus tetraspis), occurs in west and central Africa, and grows to a maximum of 190 cm (6.2 feet). This is one of its close relatives, Voay robustus, from Madagascar. It lived there until fairly recently, the most recent fossils dating to the Holocene, and may have gone extinct only 2,000 years ago. Unlike Osteolaemus, V. robustus grew to 5 m in length and had short horns on the top of the skull behind the eyes. It has been suggested that the Nile crocodile (Crocodylus niloticus), which currently lives in Madagascar, only colonised the island since the extinction of Voay.

This specimen, AMNH 3102, was collected in 1930 in southwestern Madagascar.

Sebecus icaeorhinus Simpson, 1937
Sebecidae; clade Notosuchia; Sauropsida; Chordata

It is well known that the Ancient Egyptians revered crocodiles. The god Sebek represented the Nile, as well as fertility, and was pictured as having the head of a Nile crocodile. The genus Sebecus honours Sebek. This animal was a large terrestrial carnivore, alive during the Eocene period, some 33-66 million years ago. It is not a crocodilian, unlike modern crocodiles and alligators, but a close offshoot of the ancestors of crocodiles, a member of the Notosuchia. Notosuchians were around from the Cretaceous through to the Miocene, with Sebecus being one of the last surviving genera of the group. They were a very diverse group of reptiles, some being obvious predators, while others became herbivorous.

This specimen, AMNH 3160, is a cast of a specimen collected in Argentina in 1931.

Prestosuchus chiniquensis von Huene, 1942
Prestosuchidae; "Rauisuchia"; Sauropsida; Chordata

Prestosuchus ("hurricane crocodile") was a fearsome predator that lived in Brazil during the Late Triassic (around 210 million years ago), at around the same time that dinosaurs were just beginning to diversify into saurischians and ornithischians. It is classed as a rauisuchian, a paraphyletic group of archosaurs close to crocodylomorphs (crocodilians, thalattosuchians, notosuchians, etc.), with an upright walking gait, unlike the sprawling gait of crocodilians.

This specimen, AMNH 3856, is a cast of a specimen found in Brazil in 1937, the original material housed in Germany.

Rutiodon carolinensis (Emmons, 1856)
Phytosauridae; Phytosauria; Sauropsida; Chordata

Phytosaurs ("plant reptiles", a bizarre moniker that is probably a mistake) looked remarkably like crocodiles, with the nostrils placed close to the base of the snout rather than at the tip. Rutiodon ("wrinkled tooth") was a Late Triassic phytosaur from eastern North America (North Carolina and New Jersey). This specimen, with the specimen number AMNH 1, was found in North Carolina in 1895.

Meiolania platyceps Owen, 1866
Meiolaniidae; "Testudinata"; Sauropsida; Chordata

Meiolania ("small wanderer", to distinguish from the giant monitor lizard, Megalania) was a relative of modern tortoises and turtles. It is not classified in the same order, Testudines, as that order is defined as including the common ancestor of all modern tortoises and turtles, which just about excludes Meiolania. However, as the most recent specimen of this creature dates to only 2,000 years ago, it just narrowly misses out on being defined as a testudine. The genus lived from the Oligocene until the Holocene, with this specimen, AMNH 29076 from Lord Howe Island, Australia, dating to 120,000 years BP. Instead of being able to retract its head either into its shell or alongside it like modern testudines, Meiolania had a large horned head and a spiked tail for defence against predators such as crocodiles, mekosuchines (extinct terrestrial crocodiles), and humans.

Thalassomedon hanningtoni Welles, 1943
Elasmosauridae; Plesiosauria; Sauropsida; Chordata

Thalassomedon ("sea ruler") was a long-necked plesiosaur related to Elasmosaurus. It lived in the mid-Cretaceous of North America, when the central part of the continent was underwater. This specimen is a cast of AMNH 29078 from Colorado.

Scutosaurus karpinskii (Amalitsky, 1922)
Pareiasauridae; Procolophonomorpha; Sauropsida; Chordata

Scutosaurus ("shield reptile") was a pareiasaur, a group of primitive reptiles that lived during the Permian in Russia. The Permian was the period of time directly before the Triassic: the transition between these two periods marked the greatest mass extinction of all time. Pareiasaurs like Scutosaurus were herbivorous, feeding on ferns and cycads and other vegetation. It would probably have been slow moving due to its large size, heavy armour, and short legs, and would have relied on its size when mature, and its armour, to protect itself from such predators as gorgonopsids.

This specimen is AMNH 5148, collected in northwestern Russia in the early twentieth century.

Xiphactinus audax Leidy, 1870
Ichthyodectidae; Ichthyodectiformes; Actinopterygii; Chordata

Xiphactinus ("sword ray") was a large predatory fish from the Cretaceous of central North America, colonising the same seas as Thalassomedon above. It could reach 6 m in length, and was definitely among the top predators of the time, swimming alongside mosasaurs as well as elasmosaurs. This specimen, AMNH 13102, was collected in Kansas.

Diplocaulus magnicornis Cope, 1882
Keraterpetontidae; Nectridea; Amphibia; Chordata

Diplocaulus ("double stalk") was an amphibian from Permian North America. It is well known for its boomerang-shaped head. It is often reconstructed as having a fold of skin connecting these bone wedges to the flanks, but it is argued this would have been pointless in life. It could have reached a metre in length, and is considered to be a primitive amphibian, not too closely related to salamanders. This specimen, AMNH 23175, was collected in Texas in 1895 by Charles Sternberg.

Henodus chelyops Huene, 1936
Henodontidae; Placodontia; Sauropsida; Chordata

The final photo is of Henodus ("one tooth"), a turtle-like reptile from the Late Triassic of Germany. Despite its flat turtle-like shell, and obvious turtlyness, it is a placodont, a group of sauropterygian reptiles closer to plesiosaurs than turtles. Placodonts had crushing dentition to eat molluscs and other shelled creatures. Henodus dwelled in shallow lagoons in what is now Germany.

Saturday, 30 May 2015

American Museum of Natural History: Hall of Saurischian Dinosaurs

I visited New York City last June/July, for the first time. Naturally, one of the first places I visited was the American Museum of Natural History. In the first of hopefully a short series of posts on that museum, I feature the Hall of Saurischian Dinosaurs. Saurischians are one of the two major groups of dinosaurs. The most well known members of this group include Brontosaurus, Tyrannosaurus, and the domestic chicken.

The photos below were taken at the American Museum of Natural History, New York, in June 2014, by Mo Hassan. They are presented in rough phylogenetic order.

Plateosaurus engelhardti von Meyer, 1837
Plateosauridae; Saurischia; Sauropsida; Chordata

Plateosaurus (from the Ancient Greek for"flat lizard") was one of the first dinosaurs. Non-avian dinosaurs (that is, all dinosaurs that are not birds), arose during the Triassic Period and lasted until the end of the Cretaceous Period, a stretch of time lasting around 170 million years. Among the earliest were small theropods (bipedal carnivores) like Coelophysis (see below), and Plateosaurus. It was a prosauropod - early offshoots from the branch that later led to sauropods - the long-necked dinosaurs like Brontosaurus. Plateosaurus has been known since the 1830s, when several bones were found in Germany and later identified as dinosaur bone.

Plateosaurus remains one of the best known dinosaurs as over a hundred individuals are known from many parts of Germany. The individual photographed was named Plateosaurus trossingensis Fraas, 1913, but later synonymised with the type species of the genus, P. engelhardti. Its specimen number is AMNH 6810 and was collected by Friedrich von Huene in 1925 in Trossingen in southwest Germany, and dates from the late Norian stage of the Upper Triassic.

Brontosaurus excelsus Marsh, 1879
Diplodocidae; Saurischia; Sauropsida; Chordata

You may have heard of Brontosaurus, it's got to be one of the most well known dinosaurs of all time. Except that for over a hundred years, it didn't even exist. Well, only in the sense that it has been known to science by another name. Apatosaurus ("deceptive lizard") and Brontosaurus ("thunder lizard") are both types of sauropod, both living at the same time in the same place. For most of the twentieth century they were assumed to belong to the same species, and as the name Apatosaurus was published first, due to the rules of zoological taxonomy, Brontosaurus became demoted to a synonym of Apatosaurus. A study published this year has determined that Brontosaurus is sufficiently distinct from Apatosaurus, and resurrected the name for three species previously assigned to Apatosaurus. One of these is A. excelsus, now B. excelsus, which the above pictured sauropod was identified as.

The specimen, AMNH 460, is mostly real, with the skull based on Apatosaurus louisae, and tips of tail and limbs from another specimen. It dates from 150 million years ago (Kimmeridgian/Tithonian stages of the Late Jurassic). According to the recent study (Tschopp, Mateus & Benson, 2015), which looked at individual specimens rather than species, AMNH 460 is a close relative of both Apatosaurus species and all three Brontosaurus species, but not a member of either. For now, it remains either Apatosaurus excelsus or Brontosaurus excelsus, until a new genus is erected for it if needs be.

Diplodocus longus Marsh, 1878
Diplodocidae; Saurischia; Sauropsida; Chordata

Everyone who's ever been to the Natural History Museum in London will know about Dippy the Diplodocus. Specifically, Dippy is a cast of CM 84, an almost complete skeleton of Diplodocus carnegii Hatcher, 1901, in the collections of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. The eponymous philanthropist Andrew Carnegie commissioned ten casts of CM 84 to museums around the world, including London of course. But D. carnegii was not the first species of Diplodocus to be described. D. longus is the type species, meaning it was the first species to be given the genus name Diplodocus.

This skull is specimen AMNH 969, and was collected in 1903 in Wyoming. It dates from the Kimmeridgian stage of the Late Jurassic.

Coelophysis bauri (Cope, 1887)
Coelophysidae; Saurischia; Sauropsida; Chordata

Like Plateosaurus, Coelophysis ("hollow form") is one of the earliest dinosaurs, and is the best-known early theropod. It lived in Late Triassic North America, dating back to around 200 million years ago. This specimen is a cast of CM 31374, a skull from Carnegie Museum collected in New Mexico.

Dilophosaurus wetherilli Welles, 1954
Dilophosauridae; Saurischia; Sauropsida; Chordata

If you've seen Jurassic Park (who hasn't?), you'll know Dilophosaurus as the cute, frilled, venom-spitting dinosaur that jumps into Dennis Nedry's car and subsequently kills him. Dilophosaurus ("two crested lizard") in reality was somewhat bigger than the film version, and did not have a frill or the ability to spit venom, as far as we know. It is another early theropod, dating to 193 million years ago in the Sinemurian stage of the Early Jurassic. This skull is a cast of AMNH 27376, found in Arizona in 1942.

Ceratosaurus nasicornis Marsh, 1884
Ceratosauridae; Saurischia; Sauropsida; Chordata

Ceratosaurus ("horned lizard") was a contemporary of Allosaurus from Late Jurassic North America. This skull is a cast of AMNH 27631 from Colorado.

Majungasaurus crenatissimus (Depéret, 1896)
Abelisauridae; Saurischia; Sauropsida; Chordata

Abelisaurids were a group of large theropods found mainly in the southern supercontinent Gondwana. Representatives of this family have been found in South America (e.g. Carnotaurus), India (e.g. Indosuchus), and Madagascar (e.g. Majungasaurus). They all have short heads and tiny hands and arms, making them look really, really silly. Although Majungasaurus ("lizard from Mahajanga/Majunga") has been known for more than a century, it was only since the late 90s that any good material has come out of Madagascar. Prior to that, some specimens were called Majungatholus atopus, and were thought to be the remains of pachycephalosaurs (bone-headed ornithischians).

This skull is a cast of FMNH PR 2100 collected in Madagascar, dating from the Maastrichtian stage dating to 66-70 million years ago.

Allosaurus fragilis Marsh, 1877
Allosauridae; Saurischia; Sauropsida; Chordata

Allosaurus ("different lizard") is one of the most well-known theropods from the Jurassic Period, and was among the largest from the time too. This remarkably complete specimen, AMNH 5753, represents the first free-standing mount of a theropod anywhere in the world, and is depicted tearing apart a Brontosaurus skeleton. It came from Wyoming and dates from the Kimmeridgian stage of the Late Jurassic.

Ornitholestes hermanni (Osborn, 1903)
Family incertae sedis; Saurischia; Sauropsida; Chordata

Ornitholestes ("bird thief") was another Morrison Formation theropod, believed to be a coelurosaur (an advanced group of theropods including tyrannosaurs and modern birds). This specimen is a cast of the holotype (first specimen), AMNH 619, discovered in 1900 in Wyoming, again of Kimmeridgian age.

Gorgosaurus libratus Lambe, 1914
Tyrannosauridae; Saurischia; Sauropsida; Chordata

Gorgosaurus ("fierce lizard") is a smaller and slenderer relative of Tyrannosaurus. It has previously been placed in the genus Albertosaurus, but is deemed distinct nowadays. It lived slightly earlier than Tyrannosaurus, in the Campanian stage of the Late Cretaceous. Despite being smaller than its more famous relative, it was still an apex predator.

This specimen is a cast of the skull of AMNH 5664 from Alberta. It was initially named G. sternbergi, after its discoverer, Charles Sternberg, but is now considered to be a young individual of G. libratus.

Tyrannosaurus rex Osborn, 1905
Tyrannosauridae; Saurischia; Sauropsida; Chordata

T. rex needs no introduction, so you're not getting one. This specimen is AMNH 5027, collected in Montana in 1908.

Struthiomimus altus Lambe, 1902
Ornithomimidae; Saurischia; Sauropsida; Chordata

Struthiomimus ("ostrich mimic") was a very slender dinosaur related to Ornithomimus from Campanian-Maastrichtian North America. This specimen is AMNH 5339, collected in Alberta in 1914, and displays the commonly found "death pose" seen in many theropod specimens, and which is also present in modern theropods, birds. The head and neck curl back to touch the back, in a condition similar to rigor mortis known as opisthotonus ("tension behind").

Mononykus olecranus Perle et al., 1993
Alvarezsauridae; Saurischia; Sauropsida; Chordata

One group of dinosaurs that were quite close to the ancestor of modern birds is the alvarezsaurids. Mononykus ("one claw") is one of the best known of this group. In fact, Mononykus (previously known as Mononychus before it was realised that name was already occupied by a butterfly) was considered to actually be a bird, more advanced than Archaeopteryx (see below). Mononykus got its name because of large thumb claw, and it has very reduced forelimbs.

This specimen is a mounted composite cast of two specimens, AMNH 28508 and AMNH 28498, collected at different times from different locations in Mongolia. It dates from the early Maastrichtian of the late Cretaceous (70 million years ago).

Archaeopteryx siemensii Dames, 1897
Archaeopterygidae; Saurischia; Sauropsida; Chordata

Archaeopteryx ("ancient wing") is known from around twelve exquisitely preserved specimens from Solnhofen, in Bavaria (Germany). There are now considered to be two species of Archaeopteryx: the type A. lithographica, and A. siemensii. This is a cast (AMNH 5120) of a specimen of A. siemensii known as the Berlin Specimen, as the original is housed at Humboldt Museum für Naturkunde in Berlin. It is the most complete Archaeopteryx specimen. All Archaeopteryx lived during the Tithonian in the Late Jurassic, 150-148 million years ago.

Hesperornis regalis Marsh, 1872
Hesperornithidae; Hesperornithiformes; Avialae; Chordata

Hesperornis ("western bird") was a toothed grebe-like bird that lived during the Campanian stage of the Late Cretaceous in North America and Russia. This specimen, AMNH 5100, was collected in Kansas by Charles Sternberg in 1907.

Gastornis giganteus (Cope, 1876)
Gastornithidae; Anseriformes; Aves; Chordata

The first true bird in this series of photos, Gastornis ("Gaston [Planté]'s bird") was a not-too-distant relative of ducks, geese, and swans, being a member of the order Anseriformes. Gastornithids lived during the Palaeocene and Eocene epochs, some 56-45 million years ago, hence not too long (broadly speaking) after the non-avian dinosaurs went extinct (66 million years ago). It was always considered to be a savage predator due to the shape of its bill, but recent studies on bone histology indicate it never ate meat. Gastornis giganteus used to be considered distinct enough from Eurasian Gastornis that it was placed in its own genus, Diatryma. This specimen, AMNH 6169, was collected in Wyoming in 1916.

Psilopterus australis (Moreno & Mercerat, 1891)
Phorusrhacidae; Cariamiformes; Aves; Chordata

Psilopterus ("smooth wing") was a type of phorusrhacid, birds colloquially called "terror birds" for their fearsome looking appearance and size. Psilopterus is one of the smaller members of this family though, looking more like a seriema on steroids. This skull is AMNH 9157, from Argentina, dating to the early Miocene epoch (21 million years ago).

Saurornithoides mongoliensis Osborn, 1924
Troodontidae; Saurischia; Sauropsida; Chordata

Saurornithoides ("bird-like lizard") is a troodontid from the Campanian of Mongolia. It was a small-sized big-eyed dinosaur, most likely feathered, and this is the type specimen, AMNH 6516.

Velociraptor mongoliensis Osborn, 1924
Dromaeosauridae; Saurischia; Sauropsida; Chordata

Velociraptor ("fast seizer") is another very well known dinosaur, but is much smaller than most people imagine. Blame Jurassic Park again, the animals represented in the film are closer to Deinonychus (see below) in size. Nonetheless, Velociraptor is well known from some beautifully preserved specimens from Mongolia, again from the Campanian. This skull is also the type specimen, AMNH 6515.

Deinonychus antirrhopus Ostrom, 1969
Dromaeosauridae; Saurischia; Sauropsida; Chordata

Closely related to Velociraptor, Deinonychus ("terrible claw") is known from much earlier strata (Aptian-Albian) in North America. It would have been a more fearsome creature than Velociraptor considering its size, no doubt using its switch-blade "terrible claw" to good effect. This specimen is AMNH 3015, from Montana.

Khaan mckennai Clark, Norell & Barsbold, 2001
Oviraptoridae; Saurischia; Sauropsida; Chordata

The final dinosaur in this parade is a relative of the more well known (only in the popular sense, not from the point of view of specimens) Oviraptor. They were toothless, crested, bird-like dinosaurs. Khaan was a contemporary of Velociraptor and Saurornithoides and was most likely feathered. This specimen is a cast of the original specimen IGM 100/973, housed in Ulaan Bataar, Mongolia,

Thursday, 21 May 2015

Toronto Zoo

Here's a selection of photographs from my visit to Toronto Zoo in June 2014. 

All photographs taken at Toronto Zoo, Ontario, Canada by Mo Hassan. Those not in captivity are indicated in the caption, otherwise it's safe to assume they are captive.

Wild North American red squirrel
Tamiasciurus hudsonicus (Erxleben, 1777)
Sciuridae; Rodentia; Mammalia; Chordata

Giant panda
Ailuropoda melanoleuca (David, 1869)
Ursidae; Carnivora; Mammalia; Chordata

Huon, or Matschie's, tree kangaroo
Dendrolagus matschiei Förster & Rothschild, 1907
Macropodidae; Diprotodontia; Mammalia; Chordata

Southern hairy-nosed wombat
Lasiorhinus latifrons (Owen, 1845)
Vombatidae; Diprotodontia; Mammalia; Chordata

Polar bear cub
Ursus maritimus Phipps, 1774
Ursidae; Carnivora; Mammalia; Chordata

Green aracari
Pteroglossus viridis Linnaeus, 1766
Ramphastidae; Piciformes; Aves; Chordata

Elegant crested tinamou
Eudromia elegans (Saint-Hilaire, 1832)
Tinamidae; Tinamiformes; Aves; Chordata

Plush-crested jay
Cyanocorax chrysops (Vieillot, 1818)
Corvidae; Passeriformes; Aves; Chordata

Female desert-grassland whiptail lizards
Aspidoscelis uniparens (Wright & Lowe, 1965)
Teiidae; Squamata; Sauropsida; Chordata

Easily identified as females as this species is entirely parthenogenetic (all female population reproducing by cloning with unfertilised eggs).

Nicaraguan spider monkey
Ateles geoffroyi geoffroyi Kuhl, 1820
Atelidae; Primates; Mammalia; Chordata

Wild eastern kingbird
Tyrannus tyrannus (Linnaeus, 1758)
Tyrannidae; Passeriformes; Aves; Chordata

North American raccoon
Procyon lotor (Linnaeus, 1758)
Procyonidae; Carnivora; Mammalia; Chordata

Canada lynx
Lynx canadensis (Kerr, 1792)
Felidae; Carnivora; Mammalia; Chordata

Wood bison
Bison bison athabascae Rhoads, 1897
Bovidae; Artiodactyla; Mammalia; Chordata

Wild ebony jewelwing
Calopteryx maculata (Beauvois, 1805)
Calopterygidae; Odonata; Insecta; Arthropoda

Wild trumpeter swans
Cygnus buccinator Richardson, 1832
Anatidae; Anseriformes; Aves; Chordata

American moose bull
Alces americanus (Clinton, 1822)
Cervidae; Artiodactyla; Mammalia; Chordata

Wild female and young wood ducks
Aix sponsa (Linnaeus, 1758)
Anatidae; Anseriformes; Aves; Chordata

Wild tree swallow
Tachycineta bicolor (Vieillot, 1808)
Hirundinidae; Passeriformes; Aves; Chordata

Wild male Baltimore oriole
Icterus galbula (Linnaeus, 1758)
Icteridae; Passeriformes; Aves; Chordata

Olive baboon
Papio anubis (Lesson, 1827)
Cercopithecidae; Primates; Mammalia; Chordata

Red-tailed hawk
Buteo jamaicensis (Gmelin, 1788)
Accipitridae; Accipitriformes (Falconiformes); Aves; Chordata

Wild woodchuck, or groundhog
Marmota monax rufescens Howell, 1914
Sciuridae; Rodentia; Mammalia; Chordata

Spotted crossing the hippopotamus enclosure.

Spotted-necked otter
Hydrictis maculicollis (Lichtenstein, 1839)
Mustelidae; Carnivora; Mammalia; Chordata

Female Sumatran orangutans
Pongo abelii Lesson, 1827
Hominidae; Primates; Mammalia; Chordata

Bald eagle
Haliaeetus leucocephalus (Linnaeus, 1766)
Accipitridae; Accipitriformes (Falconiformes); Aves; Chordata

Wild ring-billed gull
Larus delawarensis Ord, 1815
Laridae; Charadriiformes; Aves; Chordata