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.

Etymology
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>

Thursday, March 30, 2017

March of the Moa Part 2: Anatomy and Action

In addition to being known from multiple complete skeletons, soft tissue remains including skin, feathers, muscle tissue, and organs have been found for moa. Because of this, the life appearances and anatomy of most species is relatively well-known with abundant genetic material. Moa were comparable in in some aspects to modern flightless ratites: all share, for example, a small head mounted on a long neck which is in turn connected to a rigid torso, long legs, with a covering of long strands of fur-like feathers on their bodies. In many aspects, however, moa were quite unique with a number of characteristics not seen in their modern relatives. This blog post will highlight these characteristics.

Side-by-side skeletal mounts of Ostrich (Struthio camelus) and the
North Island Giant Moa (Dinornis novaezealandiae).
Photo taken in 1870. Wiki.

Moa beaks and skulls are larger and broader than those of modern ratites, able to deal with a wider variety of plant matter (this will be addressed in greater detail in part 3 of this series). The orbits were large and the nostrils were located at the base of the beak. moa had exceptionally well-developed sense of smell as indicated by enlarged olfactory lobes, a feature which they share with kiwis. An enhanced ability to process odors suggest that chemical communication and other was an important aspect of moa behavior: note the prominent olfactory nerve (labeled CN1) in CT image of the moa brain in the video below which was generated by WitmerLab.


For as long as moa have been known to science, most skeletal mounts and early artistic portrayals have depicted them with an Ostrich-like posture: the neck being held vertically so that the head was held high above the rest of the body. However, recent examinations of moa vertebral and cranial anatomy indicate that these birds would have carried their heads in a lowered position when at rest: the neck was normally held in a curved position so that the head was level to the back. Modern kiwis and cassowaries adopt a similar position, which is more efficient for traveling through dense forest vegetation. Moa would have only adopted an erect-neck posture when browsing, during threat displays, or when surveying to their surroundings.


Two reconstructions of the Upland Moa (Megalapteryx didinus). The left image,
illustrated by George Edward Lodge in 1907 (source) shows the bird in the outdated,
ostrich-like posture with an erect neck. The left image shows the animal in a more
realistic head-lowered posture.

Moa legs were generally longer and more robust than those of modern ratites with particularly elongated tibiotarsi (in birds, the fusion of the tibia and some of the tarsal bones) and shortened tarsometatarsi (in birds, the fusion of the three main metatarsals and some of the tarsal elements). The feet were also larger and broader with most species having four toes. Small feet and elongated lower limb segments, physical characteristics shared among modern ostriches, rheas, and emus, are associated with cursoriality and maintaining high speeds over long distances. Moa limb proportions, with their shortened distal segments, suggest that they were not built for active running although they could still move reasonably fast when they needed to. However, moa may have been better suited for maneuverability than their more fleet-footed relatives. Modern cursorial ratites, despite their great running speeds, have wide turning circles and their slender limbs make sharp turns relatively difficult: the relatively open environments which these birds tend to inhabit lessens this apparent disadvantage. The sturdier legs and shorter foot bones of moa were potentially more adept at weaving through trees and other obstacles when evading aerial predators like the Haast’s Eagle (Harpagornis moorei). Kiwis have similar limb proportions.

Hindlimb skeletons of eight ratite species scaled  to the same femur length.
From left to right: Ostrich, Heavy-footed Moa, North Island Giant Moa,
Bush Moa, Mantell's Moa, Great Spotted Kiwi, Southern Cassowary, and
Upland Moa. Note that in moa and kiwi the lower limb segments are
proportionately much shorter compared those of other ratites, in which the
tibiotarsus and  tarsometatarsus are about the same length.

All flightless ratites evolved from volant (flying) ancestors which possessed hypertrophied forelimbs (wings) and a keeled sternum which supported enlarged pectoralis muscles to facilitate powered flight. When transitioning to a more terrestrial, flightless lifestyle, the sternum lost its keel with an accompanying reduction of the pectoral musculature and of the forelimb skeleton to varying degrees.
  • Ostriches and rheas demonstrate the least forelimb reduction among flightless ratites: the reason for this is because these birds utilize their forelimbs during visual displays and to stabilize themselves when running.
  • Kiwis, emus, and cassowaries demonstrate a more extreme form of reduction in which the forelimbs have become so small that they serve no obvious function and are almost never visible from within the plumage.
  • Moa have become the only known birds to completely lack any external forelimb structure due to the absence of the tbx5 gene: the gene responsible for forming the pectoral girdle. As a result, the sole remnant of the forelimb skeleton is a tiny vestige of bone known as the scapulocoracoid (the fusion of the scapula and coracoid bones) which lies against the ribcage and is no larger than a human finger.

Three grades of forelimb reduction observed in ratites. (A) long and slender
humerus with shortened forearm elements as seen in ostriches and rheas;
(B) short, stubby forearm as seen in most flightless ratites such as emus
and cassowaries; (C) complete absence of external limb elements with the
scapula and coracoid fused to form the scapulocorocoid, a feature which is
unique to moa.

The internal anatomy of moa is still mostly unknown. However, a few unique specimens of the Eastern Moa (Emeus crassus) and Stout-legged Moa (Euryapteryx curtus) have been found with ossified tracheal rings within their body cavities revealing the form and structure of the windpipe. These two species, and potentially other members of Emeidae, possessed a convoluted windpipe. From the neck, the windpipe passed downwards on the left side of the body before doubling back on itself and then backward into the lungs, almost doubling this organ’s length. Modern birds which have this adaptation (swans, cranes, etc) are known for producing deep, resonant vocalizations: the convoluted nature of the windpipe forming a structure analogous to the tubing of certain types of wind instruments. The Tetrapod Zoology blog discusses this adaptation in greater detail hereWe can imply that moa were highly vocal animals that could produce a broad range of situation-specific calls which could be heard over great distances including contact calls, alarm calls, and mating calls. These Sandhill Cranes (video) provide a reasonable analogue for potential moa vocalizations. 

A diagram approximating the shape of the windpipe in the 
Eastern Moa (Emeus crassus).

Moa plumage is particularly well-known thanks to the discovery of numerous desiccated specimens recovered from caves throughout New Zealand. Like modern ratites, moa plumage consisted of long, shaggy, and somewhat hair-like strands for insulation and repelling water. These birds possessed cryptic coloration which was adapted to camouflage them within their respective environments, much like modern kiwis or the Kakapo (Strigops habroptilus), a flightless New Zealand parrot. Base colors ranged from light yellowish-brown to reddish-brown and many feathers were tipped in white, which would have produced a mottled or speckled effect. Such coloration was ideal for concealment and likely evolved as a defensive measure against the keen-eyed flying predators with which these birds coevolved.

Characteristic morphology and color of moa feathers which are identified to
species via ancient DNA sequences. Feathers belong to (from left to right)
Upland Moa, South Island Giant Moa, Stout-legged Moa, and Heavy-footed
Moa. Figure 3 from Rawlence et al., 2009.

The nine known species of moa ranged in size from the diminutive Bush Moa (Anomalopteryx didiformis) to the large yet lanky South Island Giant Moa (Dinornis robustus); a range of 15 to 250kg. In addition, most species display female-biased sexual dimorphism (also known as "reverse dimorphism"), that is, the females grew noticeably larger than the males. For most moa, females typically ranged from 15 to 20% larger, which is typical of modern dimorphic ratites. Members of the genus Dinornis, however, display the most extreme dimorphism seen among any terrestrial vertebrate with females growing up to three times the mass of males. The size difference is so vast, in fact, that the male morph of both Dinornis species was once thought to be a species in its own right: called the Slender Moa (D. struthoides). DNA sequencing in 2003 has since corrected this mistake and several other formerly recognized moa 'species' which had been established based on size differences were also debunked.  

Comparison of coefficients of variation for femora lengths with male:female
body mass in moa. The relative size of male (blue) to females (pink) are given
for the genera Dinornis, Pachyornis, Euryapteryx, and Emeus.
Figure 3 in Huyen et al., 2003.

Part 1: Evolution & History
Part 3: Paleoecology

References & Further Reading
Huynen L, Suzuki T, Ogura T, Watanabe Y, Millar CD, Hofreiter M, Smith C, Mirmoeini S, Lambert DM (2014). "Reconstruction and in vivo analysis of the extinct tbx5 gene from ancient wingless moa (Aves: Dinornithiformes)". BioMed Central Evolutionary Biology 14:75 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>


Rawlence NJ, Wood JR, Armstrong KN, Cooper A (2009). "DNA content and distribution in ancient feathers and potential to reconstruct the plumage of extinct avian taxa". Proceedings of the Royal Society B 276: 3395-3402 <Full Article>

Huynen L, Millar CD, Scofield RP, Lambert DM (2003). "Nuclear DNA sequences detect species limits in ancient moa". Nature 425: 175-178 <Abstract>

Thursday, March 23, 2017

Heavy-footed Moa (Pachyornis elephantopus)

The Heavy-footed Moa (Pachyornis elephantopus) was the largest member of the genus Pachyornis and the third largest species of moa overall. This exceptionally heavily-built species lived in South Island during the Pleistocene and Holocene where it fed on relatively low-quality plant matter.

Heavy-footed Moa skeleton on display at the Exhibit Museum of
Natural History, University of Michigan. Wiki.

Etymology
The genus name Pachyornis is derived from the Greek words pachys (meaning “thick”) and ornis (meaning “bird”), a reference to members of this genus being particularly heavily-built compared to other moa genera. The species name elephantopus is a combination of the Greek words elephas (meaning “elephant”) and pous (meaning “foot”). Its full scientific name therefore translates as “Elephant-legged Bird” in reference to this species’ robust skeleton with particularly thick limb elements, a trait which is further emphasized by common name “Heavy-footed Moa”.

Habitat & Distribution
Heavy-footed Moa had an extensive late Quaternary fossil record. Their preferred habitat appears to have been lowland to montane grassland, shrubland, herbfields, and forest margin environments in the eastern and southern parts of South Island. The altitudinal limit for this species appears to have been 700m above sea level as no fossils for it have been found above this point. Heavy-footed Moa underwent significant changes in relative abundance and distribution in response to environmental changes during the late Pleistocene and Holocene. Climatic and environmental fluctuations during glacial cycles caused its preferred habitat to expand and contract repeatedly, resulting in two genetically distinct populations in the northern and southern halves of South Island. Like all other moa, it held a relatively constant population size until the arrival of the Maori in the late 13th century.


Physical Attributes
The Heavy-footed Moa is the third largest species of moa behind both species of Dinornis and is the heaviest moa relative to its size. It stood up to 120cm tall at the hips and 180cm tall when fully erect and weighed up to 145kg, with females being larger than the males. The skeleton was robust with relatively thick leg bones and shortened tarsometatarsi (in birds, the foot bone formed by the fusion of the metatersals). This species is known from desiccated soft tissue remains recovered from cave sites which have preserved skin, tendons, and feathers. From these subfossil remains, we know that this species had shaggy, white-tipped feathers which would give the living animal a mottled or speckled appearance and that the skin of its lower legs were covered in non-overlapping scales like those of most birds. The beak was long, sturdy, and downturned and its overall head was shaped somewhat differently from other moa and was adapted to handle particularly tough vegetation.

Ecology & Behavior
Plant remains from within coprolites and among gizzard stones reveal that Heavy-footed Moa were generalized mixed-feeders with a diet consisting of at least 21 species of particularly fibrous grassland, shrubland, and forest margin vegetation. It grazed on various types of herbs and grasses and browsed on the branchlets of trees and shrubs. As with most of the larger moa species, the only predator of adult Heavy-footed Moa was the Haast’s Eagle (Harpagornis moorei) with the smaller Eyle’s Harrier (Circus eylesi) possibly feeding on the smaller juveniles. Evidence from coprolites further shows that this species hosted several types of taxa-specific parasites.


Heavy-footed Moa are thought to have been less abundant than other moa due to its less frequent representation in the fossil record. Females appear to outnumber males at natural fossil assemblages, suggesting that males were even less common in a given population. This relatively low number of males may be due to increased predation by Haast’s Eagles who likely targeted them more regularly due to their smaller size. Heavy-footed Moa eggs were among the largest of any moa and the only known moa embryos are also attributed to this species. The growth rate of this species is not known. It became extinct abruptly due to human overexploitation and habitat alteration.

References & Further Reading
Attard MRG, Wilson LAB, Worthy TH, Scofield P, Johnston P, Parr WCH, Wroe S (2016). "Moa diet fits the bill: virtual reconstruction incorporating mummified remains and prediction of biomechanical performance in avian giants". Proceedings of the Royal Society of London B 283: 20152043 <Full Article>

Wood JR, Wilmshurst JM, Richardson SJ, Rawlence NJ, Wagstaff SJ, Worthy TH, Cooper A (2013). "Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes)". PNAS 110(42): 16910-16915 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Oskam CL, Allentoft ME, Walter R, Scofield RP, Haile J, Holdaway RN, Bunce M, Jacomb C (2012). "Ancient DNA analyses of early archaeological sites in New Zealand reveal extreme exploitation of moa (Aves: Dinornithiformes) at all life stages". Quaternary Science Reviews 52: 41-48 <Full Article>

Rawlence NJ, Metcalf JL, Wood JR, Worthy TH, Austin JJ, Cooper A (2012). "The effect of climate and environmental change on the megafaunal moa of New Zealand in the absence of humans". Quaternary Science Reviews 50: 141-153 <Full Article>

Allentoft ME, Bunce M, Scofield RP, Hale ML, Holdaway RN (2010). "Highly skewed sex ratios and biased fossil deposition of moa: ancient DNA provides new insight on New Zealand’s extinct megafauna". Quaternary Science Reviews 29: 753–762 <Abstract>

Huynen L, Gill BJ, Millar CD, Lambert DM (2010). "Ancient DNA reveals extreme egg morphology and nesting behavior in New Zealand’s extinct moa". Proceedings of the National Academy of Science 107(37): 16201-16206 <Full Article>

Wood JR, Rawlence NJ, Rogers GM, Austin JJ, Worthy TH, Cooper A (2008). "Coprolite deposits reveal the diet and ecology of the extinct New Zealand megaherbivore moa (Aves, Dinornithiformes)". Quaternary Science Reviews 27: 2593–2602 <Abstract>


TH Worthy (1990). "An analysis of the distribution and relative abundance of moa species (Aves: Dinornithiformes)". New Zealand Journal of Zoology 17(2): 213-241 <Full Article>

Friday, March 17, 2017

Upland Moa (Megalapteryx didinus)

The Upland Moa (Megalapteryx didinus) was a small, abundant species of moa which lived in the mountainous areas of South Island. It is particularly well-represented by soft tissue remains including entire desiccated body parts with intact skin and feathers.

Upland Moa skeleton collected Mar 1987, Honeycomb Hill, Enduro, Map Grid 1385N 720E,
New Zealand. Field Collection 1982-1988. CC BY-NC-ND licence. Te Papa (S.023700)

Etymology
The Upland Moa is the only known member of the family Megalapterygidae and of the genus Megalapteryx, which is derived from the Greek words mega (meaning “big”) and apteryx (meaning “without wings”). The species name didinus means “resembling a Dodo”: didus being a Latinized generic name given to the Dodo (Raphus cucullatus) by Carolus Linnaeus. The common name for this species references its preferred habitat.

Habitat & Distribution
This species was specialized to live at the higher elevations of South Island’s alpine zone where it was common, while being rare in eastern and lowland areas. It was widespread in upland herbfields and forests up to 2,000m above sea level.

Physical Attributes
Upland Moa were a relatively small and agile moa, not as bulky as most members of Emeidae yet stockier and shorter-legged than members of Dinornithidae. It was about the size of a Greater Rhea (Rhea americana) but was more heavily-built: standing up to 95cm (3.2ft) at the hips and 160cm (5.3ft) to the top of the head, with a weight range of 17 to 40kg (37 to 90lbs). Unlike other known moa species, in which the females are noticeably larger than the males, Upland Moa do not display any obvious sexual dimorphism in regard to body size. The beak was particularly elongate and pointed. The feet were proportionally the largest of any moa with particularly long, strong toes and thick claws adapted for climbing up steep, rocky slopes and for walking across snowy terrain.


Articulated skeletal remains with dried soft tissue have been recovered from cave deposits. Among these, a complete head which included the tongue, eyeballs, part of the neck, and trachea. Feather pits in the skin show that the whole head up to the nostrils was covered in small feathers. A complete foot is also known for this species. Unlike other known moa which had scaly skin covering their lower legs, Upland Moa had feather pits extending down to the bases of the toes indicating that the whole leg and much of the foot was feathered. This is an adaptation seen among modern cold-adapted birds, such as ptarmigans (Lagopus), which provides insulation in deep snow. For the Upland Moa, this would have been ideal for the colder, windier conditions encountered at higher elevations. Upland Moa feathers were gray at the bases and deepened to a reddish-brown color toward the tips. Some of these feathers had pale-colored tips which would have given the living bird a speckled appearance similar to modern kiwis.

Desiccated type specimen of Upland Moa NHM A16
collected from Crown Range, Central Otago:
A-B, Head and neck from left( A) and right( B) side.
C-D, Right lower leg in medial (C) and lateral view (D).
Figure 5 from Rawlence et al. 2013.

Ecology & Behavior
Evidence from coprolites and gizzard contents shows that Upland Moa fed on a wide variety of alpine herbs and browsed from shrubs and trees. The presence of parasites in the coprolites such as Trematotodes, Catatropis, and Notocotylus (which typically afflict aquatic or wading birds) suggest that Upland Moa also fed around the margins of alpine lakes where they would eat aquatic vegetation. Like modern herbivores which inhabit high-altitude environments, Upland Moa would have engaged in altitudinal migrations in response to snowfall and food availability: during the autumn and winter months they would move to lowland areas where food was more accessible, returning to their upland feeding grounds during spring and summer. Predators of this species included the Haast’s Eagle (Harpagornis moorei) and the Eyles’ Harrier (Circus eylesi).


Upland Moa eggs are estimated to be about 162x111mm in size and were greenish-blue in color, unlike other moa which seem to have had white-shelled eggs. Newly-hatched chicks were able to move from the nest soon after hatching and studies of cortical bone growth show that Upland Moa took about 5 years to reach their full adult size. The fact that this species exhibited minimal dimorphism suggests that ecological segregation among sexes was limited, implying that Upland Moa were potentially more gregarious than other moa species: modern herbivores which occur in mixed-sex herds display minimal dimorphism in body size and overall appearance. The best modern analogue for reconstructing Upland Moa social behavior may be the South Island Takahe (Porphyrio hochstetteri), a flightless bird which forms family groups consisting of a monogamous breeding pair and their offspring.

Upland Moa are rarely found in archaeological sites, suggesting that they may not have been hunted as heavily as their lowland relatives. This could, in part, be due to the colder and less habitable alpine environments in which they lived: most Maori settlements were established at lower elevations. Upland Moa were therefore most likely to have been hunted by humans when they occupied lowland areas during certain times of the year. Habitat alteration may have been the primary cause of this species’ decline. It has been suggested that Upland Moa may have outlived other moa by as much as 100 years before they finally became extinct.

References & Further Reading
Attard MRG, Wilson LAB, Worthy TH, Scofield P, Johnston P, Parr WCH, Wroe S (2016). "Moa diet fits the bill: virtual reconstruction incorporating mummified remains and prediction of biomechanical performance in avian giants". Proceedings of the Royal Society of London B 283: 20152043 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Wood JR, Wilmshurst JM, Rawlence NJ, Bonner KI, Worthy TH, Kinswlla JM, Cooper A (2013). “A megafauna’s microfauna: gastrointestinal parasites of New Zealand’s extinct moa (Aves: Dinornithiformes)”. PLoS ONE 8(2): e57315 <Full Article>

Wood JR, Wilmshurst JM, Richardson SJ, Rawlence NJ, Wagstaff SJ, Worthy TH, Cooper A (2013). "Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes)". PNAS 110(42): 16910-16915 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Rawlence NJ, Wood JR, Armstrong KN, Cooper A. (2009). "DNA content and distribution in ancient feathers and potential to reconstruct the plumage of extinct avian taxa". Proceedings of the Royal Society B 7(1672): 3395-3402 <Full Article>

Gill BJ (2007). "Eggshell characteristics of moa eggs (Aves: Dinornithiformes)". Journal of the Royal Society of New Zealand 37: 139-150 <Full Article>

Turvey ST, Green OR, Holdaway RH (2005). "Cortical growth marks reveal extended juvenile development in New Zealand moa". Nature Letter 435 doi:10.1038/nature03635 : 940-944 <Abstract>

TH Worthy (1990). "An analysis of the distribution and relative abundance of moa species (Aves: Dinornithiformes)". New Zealand Journal of Zoology 17(2): 213-241 <Full Article>

Tuesday, March 14, 2017

Bush Moa (Anomalopteryx didiformis)

The Bush Moa (Anomalopteryx didiformis) was one of the smallest and most widespread moa species which lived during the Quaternary, inhabiting the forests of both of New Zealand’s main islands. This relatively slender species became extinct shortly after the arrival of the Maori.


Etymology
The Bush Moa is the only member of the genus Anomalopteryx, which is derived from the Greek words anomalus (meaning “abnormal” or “odd”) and pteryx (meaning “wing”). The species name didiformis means “of the form of the Dodo”, suggesting that Sir Richard Owen who first described this moa in 1844 likened it to the Dodo (Raphus cucullatus): another flightless bird which had gone extinct about 150 years prior to Owen’s lifetime. Taken together, the full scientific name for this species may mean “Dodo-like Bird with Abnormal Wings”. Other common names for this species include “Little Bush Moa”, “Lesser Moa”, and “Slender Bush Moa”.

Habitat & Distribution
The Bush Moa was the most widespread of all the moa species, inhabiting the closed-canopy lowland forests of both North Island and South Island, although they appear to have been more abundant on the former. It is known from complete skeletons, eggshell fragments, and soft tissue specimens including feathers and skin.

Physical Attributes
Bush Moa rivalled the Mantell’s Moa (Pachyornis geranoides) for the title of smallest moa species. Both are similar in terms of linear measurements, however the Mantell's was heavier and more robust. The Bush Moa was a slender animal with relatively long legs adapted for speed and agility, therefore making it the smallest moa in terms of mass. This species stood about 75cm (2.5ft) tall at the hips and up to 120cm (4ft) tall when fully erect, with a body mass ranging from 13 to 30kg (28 to 66lbs). The head was proportionally the largest of any moa with a relatively short, sharp-edged beak. Desiccated carcasses of this species have shown that this species was covered in yellowish-brown to pale colored feathers which measured up to 23.8mm in length.


Ecology & Behavior
The Bush Moa diet is well-known because of analyses of coprolites and gizzard contents, hall of which indicate that this species browsed on a variety of woody and fibrous plants within its forested environment. Furthermore, its sharp-edged beak was better adapted to cutting than those of other moa, and a 2016 biomechanical study has confirmed that Bush Moa fed using a unilateral clipping action. Predators of Bush Moa included the Haast’s Eagle (Harpagornis moorei), which actively hunted all species of moa, as well as the smaller Eyles’ Harrier (Circus eylesi).



Eggshell fragments attributed to this species have also been found in caves which, when reconstructed, would measure about 165 x 119mm. Nests were made in secluded locations where the males would take sole incubation duties. A 2005 study of moa cortical bone marks has shown that Bush Moa chicks took about 8 years to reach their adult size, one of the slowest growth rates known for any moa species second only to the Mantell’s Moa. Due to its small stature, Bush Moa may have been relatively gregarious compared to other moa, an advantageous behavior which limits the chances of predation on any one individual.

Like other moa, this species was the victim of overexploitation by the Maori settlers which arrived 700 to 600 years ago. Bush Moa bones have commonly been unearthed in archaeological sites, showing that the Maori actively hunted them.

An assortment of moa bones in Ngarua Caves. Note the complete Bush Moa
skeleton  in the center of this image. Wiki.

References & Further Reading
Attard MRG, Wilson LAB, Worthy TH, Scofield P, Johnston P, Parr WCH, Wroe S (2016). "Moa diet fits the bill: virtual reconstruction incorporating mummified remains and prediction of biomechanical performance in avian giants". Proceedings of the Royal Society of London B 283: 20152043 <Full Article>

Rawlence NJ, Wood JR, Scofield RP, Fraser C, Tennyson AJD (2013). "Soft-tissue specimens from pre-European extinct birds of New Zealand". Journal of the Royal Society of New Zealand DOI:10.1080/03036758.2012.704878 <Full Article>

Wood JR, Wilmshurst JM, Richardson SJ, Rawlence NJ, Wagstaff SJ, Worthy TH, Cooper A (2013). "Resolving lost herbivore community structure using coprolites of four sympatric moa species (Aves: Dinornithiformes)". PNAS 110(42): 16910-16915 <Full Article>

Wood JR, Wilmshurst JM, Worthy TH, Cooper A (2012). "First coprolite evidence for the diet of Anomalopteryx didiformis, an extinct forest ratite from New Zealand". New Zealand Journal of Ecology 36(2): 164-170 <Full Article>

Turvey ST, Green OR, Holdaway RH (2005). "Cortical growth marks reveal extended juvenile development in New Zealand moa". Nature Letter 435 doi:10.1038/nature03635 : 940-944 <Abstract>

TH Worthy (1990). "An analysis of the distribution and relative abundance of moa species (Aves: Dinornithiformes)". New Zealand Journal of Zoology 17(2): 213-241 <Full Article>

Forrest RM (1987). "A partially mummified skeleton of Anomalopteryx didiformis from Southland". Journal of the Royal Society of New Zealand 17(4): 399-408 <Full Article>