Thursday, March 8, 2018

Falkland Islands Wolf (Dusicyon australis)

The Falkland Wolf (Dusicyon australis) was a medium-sized canid endemic to the Falkland Islands of South America where it was the largest terrestrial predator and the only mammal. It also has the unfortunate distinction of being the first canid to have become extinct in historic times. 

The name Dusicyon is derived from Greek and literally translates to “foolish dog”, a reference to the apparently bold and fearless nature of the animal when it first made contact with human settlers. The species name australis means “south”, a reference to the southerly location of the Falkland Islands. The full scientific name, therefore, means “Foolish Dog of the South”. Further denoting the islands to which it is endemic, the names “Falkland Islands Wolf”, “Falkland Islands Dog”, “Falkland Islands Fox”, or “Falkland Wolf” (as is used in this blog) have been used as a common name for this species. The name “Antarctic Wolf” has also been used due to the relatively close proximity of the Falkland Islands to Antarctica. Another common name, "Warrah", is a corruption of the Guarani (an indigenous South American language) word aguará, meaning "fox". It should be noted that the terms “wolf” or “fox” are colloquialisms and do not indicate a close relationship with these canids.

Habitat & Distribution
The ancestors of the Falkland Wolf colonized what are now the East and West Falkland Islands during the last glacial maximum, about 16,000 years ago. At that time, sea levels were lower and these islands were connected to the South American mainland. After sea levels rose at the end of the Pleistocene, these dogs became isolated on the newly formed islands located 400km east of southern Argentina. Falkland Wolves are known to have occurred in all the terrestrial habitats on these islands including rocky shrub, grassland, bogs, and marshland. 

The Falkland Islands. Wiki.

Physical Attributes
Falkland Wolves were medium-sized canids about the size of a Coyote (Canis latrans) or Black-backed Jackal (Canis mesomelas), although they were shorter and more powerfully-built than either. Adults ranged from 40 to 45cm (1.3 to 1.5ft) in shoulder height, 95 to 100cm (3.1 to 3.3ft) in head-and-body length, 28 to 30cm (0.9 to 1ft) in tail length, and 10 to 25kg (22 to 55lbs) in weight. The soft, thick coat was brownish-red in color with fine white speckling and white undersides. The tail was bushy with a distinctive white tip. The head was relatively broad with hypercarnivorous dentition. DNA analysis shows that Falkland Wolves share a common ancestor with the Maned Wolf (Chrysocyon brachyurus), a long-legged canid which hunts the tall-grass savannas of South America. The common ancestor of these two species existed about 6.7 million years ago, which predates the Great American Biotic Interchange. The probable direct ancestor of the Falkland Wolf is a mainland species called Dusicyon avus, which became extinct between 3,000 and 2,500 years ago. 

Falkland Island Wolf skull. Photo from Arkive.

Ecology & Behavior
Unfortunately, The Falkland Wolf was never formally studied, and so most aspects of its behavior are unknown. It may be inferred that, like other canids, they would have formed monogamous pairs with both adults caring for their offspring. It has been said to have inhabited burrows, another common behavior among canids. Interestingly, the Falkland Wolf was the only terrestrial mammal on the Falkland Islands, and had the unique distinction of being the only known canid to have been the largest predator of its environment. Due to the absence of rodents, its diet consisted mainly of ground-nesting birds such as gulls, penguins, and geese. It is also known to have fed readily on insects. On the beaches, it may have picked off dead or unattended seal and sea lion pups and also scavenged the carcasses marine animals.

When Charles Darwin first encountered the Falkland Wolf in 1833, he noted that the population was already in decline. He predicted that its extinction would be eminent with the arrival of permanent settlers to the Falkland Islands. He also claimed that the animal would be easy to kill by hunters due to its lack of fear of humans; it was the largest predator of its environment and thus did not need to fear anything short of another Falkland Wolf. Sadly, Darwin’s observations and predictions would later prove to be correct. As the number of visits to the islands increased during the 1800s, Falkland Wolf numbers began to noticeably dwindle, particularly with the arrival of fur traders from the United States in 1839. The final blow to this species came with the arrival of Scottish settlers in the 1860s. A huge poisoning campaign was launched due to an unfounded belief that the Falkland Wolves were a threat to livestock and the species was systematically eradicated. The last known Falkland Wolf died in 1876, just 43 years after Darwin's arrival.

No conservation measures were ever made to preserve the Falkland Wolf. It was deliberately eradicated. Today, thanks to the work of the Falklands Conservation Organization, the outlook for the islands’ other residents is far more positive and it is hoped that tragic extinctions such as this will never be repeated.

1890 illustration of Falkland Wolf. Artwork by John Gerrard
Keulemans Wiki.
Thanks for reading! If you like what I do here on this blog and want to help me produce more frequent and higher quality content, please consider donating over on my Patreon page. Any amount, even just $1 is a big help and is much appreciated, and in return you get exclusive updates, blog previews and in-progress artwork, and more.

References & Further Reading
Sillero-Zubiri, C. 2015. Dusicyon australis. The IUCN Red List of Threatened Species 2015: e.T6923A82310440 <Full Article>

Francisco Prevosti F, Santiago F, Prates L, Salemme M, Martin F (2010). "Constraining the time of extinction of the South American fox Dusicyon avus (Carnivora, Canidae) during the late Holocene". Geophysical Research Abstracts, 12 (EGU2010-577-1) EGU General Assembly 2010 <Full Article>

Charles D (2000). Richard Keynes, ed. Charles Darwin's zoology notes & specimen lists from H.M.S. Beagle. Cambridge University Press. ISBN 978-0-521-46569-4. <Full Article>

Slater GJ, Thalmann O, Leonard JA, Schweizer RM, Koepfli KP, Pollinger JP, Rawlence NJ, Austin JJ, Cooper A, Wayne RK (2009). "Evolutionary history of the Falklands wolf". Current Biology 19(20): 937-938 <Full Article>

Lyras GA, Van Der Geer AAE (2003). "External brain anatomy in relation to the phylogeny of Caninae (Carnivora: Canidae)". Zoological Journal of the Linnean Society 138(4): 505–522. <Full Article>

Friday, February 16, 2018

Darwin's Ground Sloth (Mylodon darwini)

Darwin’s Ground Sloth (Mylodon darwini) is one of the earliest ground sloths to be described and is the namesake for the family Mylodontidae. This species lived in South America during the Pleistocene and is exceptionally well known thanks to the preservation of subfossil bones and soft tissue from cave sites.

Restored skull and head of Darwin's Ground Sloth (Mylodon darwini).
Reconstruction based on skull and mandible MACNC Pv 2334. 

Discovery & Etymology
Mylodon was one of the earliest ground sloth genera to be erected; after Megatherium (1796) and Megalonyx (1825). The genus name is a combination of the Greek words mylo and odous, meaning “molar” and “tooth” respectively. The species name honors the English scientist and naturalist Charles Darwin, who discovered the first known fossil of the animal during his survey expedition on the HMS Beagle. This specimen, a nearly complete lower jaw with teeth, was then given to Richard Owen who formally described it in 1839. The full scientific name translates literally as “Darwin’s Molar Tooth”, a possible reference to the animal’s homodont molariform teeth. For the purposes of this blog, I will be referring to this species as “Darwin’s Ground Sloth” or “Darwin’s Sloth”.

Holotype mandible of Darwin's Ground Sloth in occlusial view as shown
in Owen, 1839b. Scale bar = 10cm. Figure 5a from Fernicola et al., 2009

Habitat & Distribution
Darwin’s Sloth fossils are known from late Pleistocene (Lujanian) sites throughout the South American countries of Argentina, Bolivia, and Chile. Claims have been made for this species' survival well into the middle Holocene, but these are unproven. All evidence suggests that it had a broad environmental tolerance; it was capable of inhabiting arid to semiarid savannas, warm and humid forests, and even cold montane environments. This species is known to have utilized caves within its home range.

Physical Attributes
Darwin’s Sloth was a relatively large animal with a maximum estimated body mass of 1,000kg (2,200lbs). Complete skulls ranging in length from 59 to 71cm (2 to 2.3ft) in length are known. Based on this, a combined head-and-body length of 265 to 320cm (8.6 to 10.6ft) may be estimated assuming that its proportions were similar to those of the closely related Harlan’s Ground Sloth (Paramylodon harlani), which is known from multiple complete skeletons. Like other browsing ground sloths, Darwin’s Sloth had a relatively narrow skull with a sturdy snout. In fact, the species’ skull is characterized by a bony arch formed by ossified nasal cartilage. Analysis of the hand suggests that the fossorial (digging) capabilities of Darwin’s Sloth were moderate when compared to other mylodontid sloths and the animal may have renovated abandoned burrows from other animals rather than excavate its own. Although abundant postcranial material is known, a complete skeleton has never been mounted and all reconstructions of this animal are speculative and often based on a closely related species or even a combination of several species.

Articulated skull and mandible of specimen MACNC Pv 2334 in lateral view.
Note the distinctive bony nasal arch. Figure 2 from Brandoni et al., 2010.

Despite a lack of complete skeletal material, much is known about the life appearance and ecology of Darwin’s Sloth thanks to exceptionally preserved soft tissue remains recovered from dry caves, most notably from Cueva del Milodon (Mylodon Cave) in southern Chile. In addition to bones, a complete pelt, claw sheaths, and dung belonging to this species was recovered from this site. Thanks to these findings, we know that Darwin’s Ground Sloth was covered in thick, reddish-brown fur. The skin itself was thick with a network of pebble-like osteoderms embedded within it. These remains were so well-preserved, in fact, that they were initially thought to have come from a recently dead animal. This inspired several expeditions into the remote reaches of South America with the hopes of finding a living example of the species. Of course, these expeditions ended in failure and the specimens have since been dated to around 10,000 years ago (click here for a lovely write-up detailing these expeditions). However, the superb condition of this ancient soft tissue speaks to the remarkable preservation potential of cave systems.

Darwin's Sloth claw sheathes, dung, and skin on display at
Natural History Museum, London. Wiki.

Ecology & Behavior
Darwin’s Sloth has traditionally been considered to be a grazer which lived in open grassland environments. This interpretation was due to the plant remains found within the preserved dung from Cueva del Milodon, which show that the individual that left them fed mostly on grasses and sedges near the time the dung was deposited. While compelling, this finding is not a reliable indicator of the year-round dietary regime for the species. Recent biomechanical and functional morphological studies suggest that Darwin’s Sloth was instead a mixed or selective feeder which could utilize a broad range of plants depending on the time of year and situation. Perhaps, like modern mixed feeders, its diet was more graze-based during wetter periods when the grass is green and growing, and then shifted to be more browse-based during drier periods.

The animals which have been found in association with Darwin’s Sloth are indicative of grassland, savanna, or open woodland habitats with ready access to water. These include such animals as gomphotheres (Stegomastodon), deer (Morenelaphus and Antifer), notoungulates (Toxodon), litopterns (Macrauchenia), horses (Hippidion and Equus), other ground sloths (Megatherium), and tapirs (Tapirus). Possible predators of Darwin’s Sloth included Jaguar (Panthera onca) and Southern Sabertooth (Smilodon populator). We know that it interacted with and was probably hunted by humans during the late Pleistocene; the preserved pelt mentioned above shows the telltale signs of having been removed and worked by humans. Whether or not the humans actually killed this sloth is unknown, but the skinning of such an animal was undoubtedly difficult due to the thickness of the skin and the embedded network of osteoderms which must have served a protective function similar to chainmail. This may be the reason the pelt was ultimately left in the cave and not taken by those who processed it.

A piece of preserved skin from Darwin's Sloth shown from below. Note the
random and densely arranged osteoderms. Such an attribute was likely an
anti-predator adaptation designed to negate piercing attacks from teeth and
claws, or spears and arrows. Image source.

Thanks for reading! If you like what I do here on this blog and want to help me produce more frequent and higher quality content, please consider donating over on my Patreon page. Any amount, even just $1 is a big help and is much appreciated, and in return you get exclusive updates, blog previews and in-progress artwork, and more.

References & Distribution
Farina RA, Czerwonogora A, Giacomo MD (2014). "Splendid oddness: revisiting the curious trophic relationships of South American Pleistocene mammals and their abundance". Anais da Academia Brasileira de Ciências 86(1): 311-331 <Full Article>

Borrero LA, Martin FM (2012). "Taphonomic observations on ground sloth bone and dung from Cueva del Milodón, Ultima Esperanza, Chile: 100 years of research history". Quaternary International 278: 3-11 <Abstract>

Brandoni D, Ferrero BS, Brunetto E (2010). "Mylodon darwini Owen (Xenarthra, Mylodontinae) from the Late Pleistocene of Mesopotamia, Argentina, with remarks on individual variability, paleobiology, paleobiogeography, and paleoenvironment". Journal of Vertebrate Paleontology 30(5): 1547-1558 <Abstract>

"Does the ground sloth, Mylodon darwinii, still survive in South America?" R Barnett and S Sylvester. Deposits (2010), Issue 23, P8-11 <Full Article>

Fernicola JC, Vizcaino F, de Iuliis G (2009), "The fossil mammals collected by Charles Darwin in South America during his travels on board the HMS Beagle". Revista de la Asociatión Geológica Argentina. 64(1): 147-59 <Full Article>

Vizcaino SF, Farina RA, Fernicola JC (2009). "Young Darwin and the ecology and extinction of Pleistocene South American fossil mammals". Revista de la Asociatión Geológica Argentina 64(1): 160-169 <Full Article>

Bargo MS, Toledo N, Vizcaino SF (2006). "Muzzle of South American Pleistocene ground sloths (Xenarthra, Tardigrada)". Journal of Morphology 267: 248-263 <Full Article>

Owen R (1840). ‘Part I. Fossil Mammalia’, in C. R. Darwin (ed.), "The zoology of the voyage of H.M.S. Beagle, under the command of captain Fitzroy, R. N., during the years 1832 to 1836" (London: Smith, Elder and Co.) <Full Article>

Saturday, January 20, 2018

Sphenisciformes: the Penguins

Penguins are flightless, marine birds belonging to the order Sphenisciformes in the family Spheniscidae. They have existed since the beginning of the Cenozoic with roots possibly dating back to the late Cretaceous, and they appear to have always been restricted to the Southern Hemisphere; both modern penguins and their extinct relatives are distributed along the coasts of Antarctica, Australia, New Zealand, sub-Saharan Africa, and South America.
A pair of Emperor Penguins (Aptenodytes forsteri) tobogganing across
an Antarctic snowscape. Wiki.
The Paleogene fossil record of penguins has been intensively studied in the last few decades with numerous new taxa having been described during that time, with argueably the most interesting discoveries coming out of New Zealand. Although the penguin lineage is believed to have split away from other birds as early as the late Cretaceous (71mya), the earliest-known and most basal penguins date back to the early to middle Paleocene (62 to 58mya) and belong to the genus Waimanu from New Zealand. The South American genus Perudyptes and a slightly older, unnamed taxon, demonstrate that penguins had expanded their range to encompass the entire southern Pacific Ocean by the middle Eocene and were probably present throughout the Atlantic Ocean as well. There are four accepted penguin subfamilies (discussed below), only one of which is still alive today.

Map showing the collective distribution of modern penguins.
 Penguins throughout their evolutionary history appear to have
been confined to the Southern Hemisphere, so this distribution
map is also applicable to fossil penguins. Wiki.
The Palaeeudyptinae, or “giant penguins”, are the most well-studied of the extinct penguin subfamilies. The earliest known member, Crossvallia unienwillia, lived during the late Paleocene (59.2–56mya) in what is now Antarctica, and therefore would have coexisted with basal penguins like Waimanu. The group persisted throughout the Paleogene and until the late Oligocene, and potentially even lasting until the middle Miocene if the tentatively placed Anthropodyptes proves to be a true member. Palaeeudyptines differ from modern penguins in a number of aspects. For example, the forelimb had not yet developed into a rigid flipper and would have retained a degree of flexibility. The beak also differs from those of modern penguins in being relatively long and spear-like, similar to that of a heron.

By far the most frequent topic addressed when discussing members of Palaeeudyptinae, is body size. True to their colloquial name, these early Cenozoic penguins were quite large by modern standards; the 20 species of modern penguin range in size from the 40cm tall and 1kg Little Blue Penguin (Eudyptula minor), up to the 110cm tall and 35kg Emperor Penguin (Aptenodytes forsteri). The early palaeeudyptine Crossvallia unienwillia was only slightly larger than an Emperor Penguin with much larger penguins, with body lengths of over 130cm, occurring from the middle Paleocene to the late Oligocene. Due to the often fragmentary and incomplete nature of penguin fossils, physical aspects such as body size and mass must be calculated by measuring individual bones and scaling them against modern specimens. Through this method, lengths of 180cm and 160cm have been calculated for Anthropornis nordenskjoeldi and Palaeeudyptes klekowskii respectively, both being widely regarded as the largest penguins known to have ever lived (the latter even being given the common name of “Colossus Penguin”).

Giant penguins appear to have become extinct early in the Neogene. The reason for their disappearance is not currently understood, although a likely explanation may be a combination of climatic changes and feeding competition from pinnipeds (seals, sea lions, and walruses) which were undergoing an adaptive radiation at the time these giant penguins had declined.

Palaeospheniscinae & Paraptenodytinae
Smaller than the large-bodied palaeeudyptines with whom they coexisted for a time, the Palaeospheniscinae and Paraptenodytinae may have been the ecological analogues of the modern spheniscine penguins, though they were probably not directly ancestral to them. Both subfamilies are relatively poorly understood at the timing of this blog post. Palaeospheniscines, also known as “slender-footed penguins”, contain five species within the genus Palaeospheniscus. They were small to medium-sized penguins that ranged in body length from 50 to 75cm, and occurred from the early Miocene to early Pliocene of southern Africa and South America. Paraptenodytines, also known as the “stout-footed penguins”, contains four known species within the genera Arthrodytes and Paraptenodytes. These occurred from the late Eocene to the middle Miocene of South America

The group containing all modern penguins, all of which belong to the subfamily Spheniscinae, arose during the late Paleogene and recognizable members of today’s genera began to appear during the middle Miocene (14 to 13mya). The radiation of this group appears to correspond to two episodes of global climatic cooling.

Examples of each of the modern genera within the penguin subfamily Sheniscinae.
From left-to-right and top-to-bottom: King Penguin (Aptenodytes patagonicus),
Adelie Penguin (Pygoscelis adeliae), Megallanic Penguin (Spheniscus magellanicus),
Little Blue Penguin (Eudyptula minor), Macaroni Penguin (Eudyptes chrysolophus),
Yellow-eyed Penguin (Megadyptes antipodes).

Among modern penguins, the genus Aptenodytes (“great penguins”) are the most basal, with DNA evidence showing that these birds split from other spheniscines around 40mya. The earliest known fossil evidence for this genus comes from the early Pliocene of New Zealand and ascribed to the species A. ridgeni. The two modern members of the genus are characterized by yellow-orange neck, breast, and beak patches. Chicks are almost naked upon hatching and brooding adults incubate their eggs on their feet beneath a specialized fold of skin.

The genus Pygoscelis (“brush-tailed penguins”) are the next to diverge with DNA evidence showing that a split occurred at about 38mya and are said to most closely resemble the common ancestor of the Spheniscinae in physical form. Fossils from the genus date to the late Miocene of South America and New Zealand. There are three modern species which breed in Antarctica and southern South America.

The oldest fossils of the genus Spheniscus (“banded penguins”) date back to the middle Miocene. There are four modern species distributed through southern Africa and the southern and western coasts of South America up to the equatorial islands of Galapagos. Members of the genus are characterized by a single band of black that runs around their bodies bordering their black dorsal coloring, black beaks with a small vertical white band, distinct spots on their bellies, and a small patch of unfeathered or thinly feathered skin around their eyes that can be either white or pink. All members of this genus raise their young in nests situated in burrows or natural depressions in the earth. They are also renowned for their loud, braying vocalizations which earn them the nickname of the "jack-ass penguins".

The genus Eudyptula (“little penguins”) contains three modern species which are distributed through southern Australia and New Zealand. They are burrow-nesters distinguished by their small body size and iridescent dorsal plumage which gives them a bluish-black appearance.

Members of the genus Eudyptes (“crested penguins”) are characterized by their hair-like yellow ornamental head feathers and their reddish-colored beaks. This is the most specious of the modern penguin genera, containing eight species. These form a clade with the New Zealand endemic genus Megadyptes, which has a single living species and one recently extinct after first contact with the Maori. The two genera apparently diverged from each other during the middle Miocene (15 or 14mya) and the modern species of Eudyptes all radiated between the late Miocene and late Pliocene (about 8 to 3mya).

Skeleton & Movement
Penguins are superbly adapted for an aquatic environment and are remarkably swift and agile when traveling through the water (video). Unlike volant (flying) birds which have lightweight, hollowed bones to reduce body weight, penguin bones are solid and heavy which decreases buoyancy, making diving easier. Unlike other flightless birds, the penguin sternum is keeled to support well-developed pectoral musculature. The flight stroke of the wings has been modified into a swimming stroke, enabling these birds to “fly” through the water. The wings of their ancestors have been modified into rigid flippers, which has been achieved by the broadening, flattening, and densification of the bones of the forelimb. While swimming, the feet and tail trail backwards and function as steering aids or rudders. The body itself is fusiform in shape for streamlining.
Articulated skeleton of the Magellanic Penguin (Sheniscus magellanicus)
shown in swimming posture. Wiki.

In contrast to their efficient aquatic locomotion, terrestrial locomotion can be rather slow and clumsy (video). Penguins primarily adopt an upright waddling gait during terrestrial locomotion during which they use their flippers and tails to maintain balance and an upright stance. A hopping motion is utilized for travel over uneven or rocky terrain. The penguin tarsometatarsus (the fusion of three metatarsals and some of the tarsal bones in birds) is very distinctive in that it is extremely short, broad, and flat. possibly to strengthen the foot. This unique shape was present in penguins by the middle Paleocene, as demonstrated by Anthropornis. This shape may correlate functionally with the aforementioned upright posture and gait adopted by modern penguins. The one known subversion of this morphology is the very basal genus Waimanu, which was contemporaneous with Anthropornis but had a tarsometatarsus that was morphologically more comparable to that of a cormorant. This suggests that these archaic penguins had a somewhat different style of terrestrial locomotion and that they probably relied more on their feet for propulsion.

Foot bones of three penguin genera, two extinct and one modern. Compare
and contrast the morphology of the tarsometatarsi between
Anthropornis (a-c), Waimanu (f-g), and Aptendytes (j-k).
Figure 1 from Mayr et al. (2017).

Skin & Feathers
Modern penguins possess a layer of fat, or blubber, several centimeters thick for insulation in cold waters. Given the largely tropical to subtropical conditions of the Paleogene, it is hard to say whether early penguins such as the giant palaeeupytines would have needed this extra layer of insulation. If not, these penguins would have appeared relatively slender compared to modern penguins despite many of them being considerably larger. What is almost certain is that, like their modern relatives, fossil penguins had a dense covering of short, rigid feathers. This plumage insulates penguins against cold air and water by trapping air near the skin. Waterproofing is achieved through the application of a special oil during grooming. When hot, penguins ruffle their feathers to allow cool air to reach their skin, thus lowering the body temperature.

Preserved skin and feathers are known for the late Eocene species Inkayacu paracasensis confirms that the penguin feather morphology was in development very early in the group’s evolutionary history. The feathers of the flipper and body, which were densely packed together, had large shafts that made them very rigid. The feathers were also short compared to those of modern penguins, with a maximum length of 3cm. This, again, may reflect the warm Paleogene environment in which these early penguins lived and the need for insulation; I. paracasensis was a larger animal which lived in tropical waters, while modern penguins are smaller and, with the exception of the Galapagos Penguin (Spheniscus mendiculus), generally inhabit colder Antarctic and Subantarctic waters.

Photograph showing the wing feathering of the late Eocene Inkayacu paracasensis
(scale = 1 cm). Figure 2 from Clarke et al. (2010).

All modern penguins have a countershaded color scheme as adults, with black or dark brown dorsal plumage and white ventral plumage. This coloration provides camouflage when viewed from the top and bottom; a predator looking up from below has difficulty distinguishing between a white penguin underside and the reflective water at the surface, while the dark plumage on the back blends the darker water seen at deeper depths. The known feathers for I. paracasensis are different in that they appear to have been gray or reddish-brown in color as determined by the shape and structure of the melanosomes. It is unclear how these colors were distributed; they may have covered the whole body or perhaps this penguin was similar to the modern Aptenodytes in having special identifying markings while the rest of the body was the more conventional black-and-white pattern. Nonetheless, this fossil eludes to the potential variability that could have existed in the plumage of fossil penguins.

Penguin eyes are specialized for underwater vision and the sense of sight is their primary means of hunting. The sense of hearing is said to be average by the standards of other birds, but nonetheless appears to be sensitive enough for individuals to identify and locate their mates and offspring within huge, densely populated nesting colonies. The first ever study published study to determine the importance of scent for individual recognition in birds demonstrated that Humbolt Penguins (Speniscus humbolti) are able to discern familial and non-familial odors, a finding which holds many implications for penguin social behavior. Interestingly, endocasts of the braincases of multiple genera demonstrate that fossil penguins such as Paraptenodytes had larger olfactory lobes than modern penguins, suggesting that the sense of smell was even more important to them behaviorally.

Endocasts of the brain (blue) and semicircular canals (pink) in several
extinct and modern penguins:
(A) an unnamed fossil from Atarctica
(B) Paraptenodytes antarcticus
(C) Emperor Penguin (Aptenodytes forsteri)
(D) African Penguin (Spheniscus demersus)
(E) Magellanic Penguin (Spheniscus magellanicus)
(F) Little Blue Penguin (Eudyptula minor)
(G) Chinstrap Penguin (Pygoscelis antarctica)
(H) Adélie Penguin (Pygoscelis adeliae)
Figure 9 from Tambussi et al. (2015)

Thanks for reading! If you like what I do here on this blog and want to help me produce more frequent and higher quality content, please consider donating over on my Patreon page. Any amount, even just $1 is a big help and is much appreciated, and in return you get exclusive updates, blog previews and in-progress artwork, and more.

References & Further Reading
Mayr G, De Pietri VL, Scofield PR (2017). "A new fossil from the mid-Paleocene of New Zealand reveals an unexpected diversity of world’s oldest penguins". The Science of Nature 104(9): DOI 10.1007/s00114-017-1441-0 <Abstract>

Mayr G, Scofield PR, De Pietri VL, Tennyson AJD (2017). "A Paleocene penguin from New Zealand substantiates multiple origins of gigantism in fossil Sphenisciformes". Nature Communications 9(1927): DOI: 10.1038/s41467-017-01959-6 <Full Article>

Gavryushkina A, Heath TA, Ksepka DT, Stadler T, Welch D, Drummond AJ (2017). "Bayesian total evidence dating reveals the recent crown radiation of penguins". Systematic Biology 66(1): 57-73 <Full Article>

Tambussi CP, Degrange FJ, Ksepka DT (2015). "Endocranial anatomy of Antarctic Eocene stem penguins: implications for sensory system evolution in Sphenisciformes (Aves)". Journal of Vertebrate Paleontology: e981635 <Abstract>

Coffin HR, Watters JV, Mateo JM (2011). "Odor-based recognition of familiar and related conspecifics: a first test conducted on captive Humbolt penguins (Spheniscus humbolti)". PLoS ONE 6(9): e25003 <Full Article>

Clarke JA, Ksepka DT, Salas-Gismondi R, Altamirano AJ, Shawkey MD, D'Alba L, Vinther J, DeVries TJ, Baby P (2010). "Fossil evidence for evolution of the shape and color of penguin feathers". Science 330(6006): 954-957 <Full Article>

Baker AJ, Pereira SL, Haddrath OP, Edge KA (2006). "Multiple gene evidence for expansion of extant penguins out of Antarctica due to global cooling". Proceedings of the Royal Society B 273: 11-17 <Full Article>

Slack KE, Jones CM, Ando T, Harrison Gl, Fordyce RE, Arnason U, Penny D (2006). "Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution". Molecular Biology and Evolution 23(6): 1144-1155 <Full Article>

Ksepka DT, Bertelli S, Giannini NP (2006). "The phylogeny of the living and fossil Sphenisciformes (penguins)". Cladistics 22(5): 412-441 <Abstract>

Jouventin P, Aubin T, Lengangne T (1999). "Finding a parent in a king penguin colony: the acoustic system of individual recognition". Animal Behavior 57(6): 1175-1183 <Abstract>

Wednesday, November 15, 2017

Documentary Review: Walking with Beasts

Walking with Beasts (WWB) is a 6-episode miniseries which aired in late 2001 as a direct sequel to Walking with Dinosaurs (WWD). It was produced by BBC Natural History Unit and distributed by BBC Worldwide. In the United Kingdom, each of the six episodes aired on a weekly basis from November 15th to December 20th. In the United States, where it was retitled “Walking with Prehistoric Beasts”, these individual episodes were edited together and presented as a single 3-hour long documentary in December of the same year on Discovery Channel. The UK and US broadcast versions of the series were narrated by Kenneth Branagh and Stockard Channing respectively.

As with WWD, the narrative of WWB is presented in the style of a traditional nature documentary. Empty landscapes were filmed in various locations around the world and computer-generated animals were inserted later, shown interacting with the environments and with other animals. Animatronic models were used mostly for closeup shots of the head and life-sized puppets were built for carcasses. Each episode follows the life of a specific animal which serves as a window through which the audience views the world around it and the creatures with which it coexists. The nature documentary style is further reinforced by a few scenes in which the CGI animals interact directly or indirectly with the camera, such as when a young indricothere aggressively charges and knocks over the camera or when a rock thrown by an australopithecine collides with the camera lens cracking it.

Animals featured within Walking with Beasts. Source

While the main focus of the series is on its animal subjects, each episode indirectly addresses an important theme or concept.
  • Episode 1 (New Dawn) touches on the recovery and diversification of mammals after the K/Pg extinction, in the process highlighting some of the adaptations which enabled their success.
  • Episode 2 (Whale Killer) introduces the global climate change that was set in motion largely by the isolation of Antarctica and the subsequent formation of the Antarctic Circumpolar Current, an event which would become a significant driving factor in mammalian evolution through the rest of the Cenozoic.
  • Episode 3 (Land of Giants) shows how mammals recovered and adapted after the Grande Coupure, or the Eocene-Oligocene extinction event, which was likely caused by the aforementioned climatic changes shown in the previous episode.
  • Episode 4 (Next of Kin) depicts the origins of the human lineage as well as establishing how much more familiar the mammalian fauna of the Pliocene would be to us compared to earlier episodes.
  • Episode 5 (Sabretooth) touches on the Great American Biotic Interchange (GABI) by showcasing some of the animals that evolved in isolation on the former island continent of South America and how invading predators from North America changed its ecology.
  • Episode 6 (Mammoth Journey) shows how certain types of mammals have adapted to survive at northern latitudes during glacial cycles, as well as showing how humans have progressed and spread from their ancestral homeland.

Anamatronic entelodont head used in episode 3 of
Walking with Beasts. Source
WWB set a major milestone among paleo-documentaries. While most, including WWD, focused on dinosaurs and other animals of the Mesozoic, WWB places its focus exclusively on the Cenozoic Era. Due to the popularity of (non-avian) dinosaurs, the period after their extinction and the animals that lived during that time have remained relatively unknown to the general public with the exception of more “mainstream” creatures such as sabertooths, mammoths, sloths, and hominids. While much focus is indeed placed on these animals in the latter half of the series, we are also introduced to a variety of interesting creatures which had never before been portrayed on television, or at least not with such attention to detail. In the first episode alone, we are introduced to such creatures as the bipedal mesocarnivore Leptictidium, the walking whale Ambulocetus, and the cat-sized horse Propalaeotherium.

Leptictidium is one of many animals to be depicted on television
for the first time in Walking with Beasts. Source
Watching this series as a young paleontology enthusiast had a profound impact on me. I was captivated by the selection of animals being depicted, most of which I had never heard of before. WWB series sparked in my then 13 year old mind a desire to learn more about these creatures and ultimately led me to shift my research interests away from dinosaurs and toward Cenozoic mammals. Apart from the improved visual effects and storytelling, I found the WWB soundtrack to be much more enjoyable than that of WWD, and to this day I often play it on loop while drawing or writing. In fact, the animals presented within WWB are generally more anatomically accurate in their movement and appearance because most of them have living relatives that could be used as analogues. The series has aged relatively well and is a good introduction to Cenozoic paleontology despite its flaws/inaccuracies, most of which can be attributed to budgetary constraints or limited knowledge at the time of production. These will be elaborated upon in smaller posts in which I will review each episode on its own merits. I will, however, briefly mention a few general problems that I noticed throughout the series;
  • The Paleocene and Miocene are completely skipped over in WWB. While this omission is unfortunate, the decision to do so is understandable from a practical standpoint. The Paleocene is the least understood portion of the Cenozoic. Meanwhile, the Miocene comprises a massive 18 million year gap with many interesting and well-known faunas across the world to choose from, and is thus probably deserving of its own documentary unto itself.
  • As with all the Walking with miniseries, WWB regularly utilizes recycled animation or repurposed creature models. At numerous points, specific clips may be repeated two or more times over the course of a given episode. At others, CGI models may be given a different skin and reused in a later episode. Similarly, the juveniles of some species are simply shrunken down replicas of the adult models. Such “cloning” is fortunately mostly limited to those animals to which less screen time is given and much more differentiation can be seen in those that are on screen most frequently, with some even showing sexually dimorphic traits. Other problems with the models include some shrink-wrapping in the more short-haired/feathered animals, and keen-eyed viewers will note some minor differences in appearance between the CGI animals and their animatronic counterparts.
  • What I found most memorable about the Discovery Channel broadcast of WWB were the brief and informative paleontology segments that were interspersed before commercial breaks and between episodes. In these segments, scientists would give brief explanations of the fossil evidence, thus providing additional information and credibility to what was being portrayed in the main program. These segments were, unfortunately, not included in the DVD release of the series. The decision to not include these segments always confused me, especially since later programs like When Dinosaurs Roamed America and Dinosaur Planet have shown that such a format works quite well (though it should be noted that these programs were produced by Discovery Channel and not BBC).

Side-by-side comparison between the Smilodon mode used in episode 5 and
the Cave Lion from episode 6. Source1 & Source2
These problems do not distract from the stories being presented. It is a worthy successor to its critically acclaimed predecessor WWD and improves upon the formula in many ways. In terms of its coverage and portrayal Cenozoic animals, WWB greatly outclasses older documentaries such as Paleoworld (1994-1997) and Extinct (2001), the latter of which dabbled in CG animated storytelling. Overall, I recommend WWB to anyone who is interested in prehistoric life and I will be using this series as a benchmark when reviewing other paleo-documentaries.

Other Reviews

Sunday, April 16, 2017

Minorca Giant Rabbit (Nuralagus rex)

The Minorca Giant Rabbit (Nuralagus rex) lived on the island of Minorca off the coast of Spain during the Pliocene. Among other unique characteristics, this species holds the record as the largest lagomorph yet discovered. It was also the only lagomorph to become the largest mammalian herbivore of its environment.

Reconstruction of Nuralagus rex based on a selection of bones with
best-fitting articular surfaces. Shown alongside the modern European Rabbit
(Oryctolagus cuniculus) for scale. Figure 3 from Quintana et al., 2011.

The Minorca Giant Rabbit was described in 2011 and is known from abundant skeletal remains. Nura is the ancient Phoenician name for the island of Minorca, and lagos is the Greek word for hare or rabbit. Its species name rex is the Latin word for king, which is a reference to this species great size compared to other lagomorphs. “The King Rabbit of Minorca”. For the purposes of this blog I will be referring to this species as the “Minorca Giant Rabbit” or simply “Minorca Rabbit”.

Habitat & Distribution
Thought to have descended from mainland European rabbits of the genus Alilepus, Minorca Rabbits were, as their name suggests, endemic to the small island of Minorca in the Mediterranean Sea off the coast of Spain. Evolving on a small island which lacked large predators or large-bodied competing herbivores allowed these rabbits to rapidly grow in size and become the largest herbivores in their habitat. The species is known from Pliocene deposits and is thought to have become extinct by the early Pleistocene.

Physical Attributes
Minorca Rabbits differed in numerous ways to modern rabbits, the most obvious difference being its great size. It stood about 50cm high at the shoulder and had an estimated average body mass of 12kg (27lbs), making it more than 10 times heavier than the largest modern rabbits and over 2 times heavier than the largest hares. The modern Amami Rabbit (Pentalagus furnessi) from Japan shares many physical traits with its extinct cousin, albeit to a lesser degree. Most notably, the cursorial adaptations possessed by their mainland relatives have been lost. The hindlimbs were shorter and more robust with broad, plantigrade feet: modern rabbits have long hindlimbs with narrow, shock-absorbing feet. The vertebral column of the Minorca Rabbit was also shorter and less flexible which would further reduce its stride length. When it needed to move quickly it would do so in more of a loping conventional gait probably similar to that of a large mustelid rather than utilizing the hopping gait employed by other rabbits. Furthermore, the body was bulky and the volume of the ribcage shows that the heart and lungs were proportionally small: in cursorial mammals, the ribcage is typically expanded and these organs are often enlarged to maximize circulation and airflow during a run. The skull, eyes, and ears are all notably smaller in proportion to the rest of the body than it is in modern rabbits, suggesting that vision and hearing was somewhat reduced; this is not a severe handicap in an environment which lacks large predators. Large, curved claws and robust forearm bones indicate that Minorca Rabbits were particularly skilled at digging.

Ecology & Behavior
Like many modern rabbits and hares, Minorca Rabbits likely inhabited extensive burrow systems, excavated by their well-developed claws and forelimbs. These fossorial attributes were also potentially used to dig for plant roots and other underground food resources. Although it is unknown what plants it habitually preferred, this species was most likely a mixed-feeder that grazed and browsed on most of the plants within all habitats on the island. Minorca Rabbits had no known terrestrial predators, although juveniles were potentially at risk from predatory birds.

References & Further Reading
Quintana J, Köhler M, Moyà-Solà S (2011). “Nuralagus rex, gen. et sp. nov., an endemic insular giant rabbit from the Neogene of Minorca (Balearic Islands, Spain)”. Journal of Vertebrate Paleontology 31(2):231–240 <Full Article>