March of the Moa Part 1: Evolution and History on New Zealand

March of the Moa Part 1: Evolution and History on New Zealand

Os moa (Dinornithiformes) são um grupo de aves que não voam e que viveram na Nova Zelândia a partir do Mioceno médio e sobreviveram até o final do século 14 ao início do 15: por volta da época a Europa estava passando da Idade Média para o período da Renascença. 

 

Eles eram os maiores e mais influentes vertebrados dentro dos ecossistemas terrestres da Nova Zelândia e havia 9 espécies em 6 gêneros e 3 famílias, com a chegada dos primeiros colonos humanos 700 anos atrás. 

 

Mais informações são conhecidas sobre o moa do que qualquer outro grupo de animais completamente extinto, desde esqueletos completos e cascas de ovos até tecidos moles preservados contendo DNA antigo sendo coletado. Este post, portanto, servirá como a primeira entrada em uma série de 5 partes, resumindo nosso entendimento atual dessas grandes aves.

Skeleton of the South Island Giant Moa (Dinornis robustus)
on display at the Yorkshire Museum, England. Wiki.

Antes de 2010, acreditava-se que os moa eram mais intimamente relacionados a emus e cassowaries australianos entre as aves modernas. Desde então, percebeu-se que os parentes vivos mais próximos de moa são os tinamous (Tinamidae): uma família de pequenos pássaros terrestres sul-americanos que se assemelham a aves de caça. É um mistério como essas aves sul-americanas, que são relativamente fracas, conseguem cruzar os 12.304 km de mar aberto para chegar às ilhas da Nova Zelândia. Talvez tenham chegado de ilha em ilha ou rafting no curso de milhões de anos. Outra possibilidade é que o tinamous, ou um parente próximo, já existisse na Nova Zelândia no início do Oligoceno quando havia menos distância entre a Nova Zelândia e a Antártida, com apenas um mar raso separando-os, enquanto a própria Antártida ainda estava conectada à América do Sul.

 

Esta última hipótese é apoiada pela presença de tartarugas meiolanóides e pleurodeais, crocodilos mekosuchinos e morcegos mystacinid que vivem na Nova Zelândia durante o início do Mioceno, todos com origem sul-americana ou australiana e que provavelmente não chegaram ao atravessar o oceano profundo. Uma vez estabelecida na Nova Zelândia, no entanto, a moa ancestral passou por uma notável radiação adaptativa, assumindo o papel de herbívoros terrestres médios a grandes na ausência de competidores de mamíferos.

An Elegant-crested Tinamou (Eudromia elegans), one of many species
of volant, ground-dwelling birds from Central and South America. Tinamou
are the closest living relatives of the moa. Wiki.

The exact timing of when the moa ancestor first arrived in New Zealand is up for debate, but the earliest definitive moa fossils are known from the early to late Miocene Saint Bathans Fauna. By this period, moa were already large-sized, flightless, and had similar skeletal anatomy to that of their more recent relatives, implying that their origin and arrival to New Zealand was much earlier than this. The radiation of the 9 Holocene species occurred primarily in South Island and was influenced by the accelerated uplifting of the Southern Alps during the late Miocene (6mya), an event which altered New Zealand’s climate and created new biomes which encouraged the evolution of new species to exploit them.  South Island, the larger of the two main islands of New Zealand, has three main habitat zones:

1. The colder highlands of the Southern Alps run from the north to the south of the island, influencing the rainfall and vegetation on either side.
2. The land to the west of the Southern Alps is densely-forested with high rainfall,
3. To the east of the mountains lay drier woodlands, shrublands, and grasslands which comprise much of the lowland area.

North Island experiences high rainfall and is dominated by deciduous forest habitat much like the western lowland area of South Island, while the land closer to the southern coast is drier and more open. The more diverse range of habitats of South Island combined with its larger land area (150,437km² to North Island's 113,729km²) explains why moa diversity is highest on South Island: 7 of the 9 species lived (5 of which being endemics) lived on South Island while just 4 species (with 2 endemics) inhabited North Island.

New Zealand split from the supercontinent of Gondwana during the late Cretaceous
and is currently situated about 1,500km east of Australia and 5,000km north of Antarctica.
 Because of its remoteness, it was the last habitable landmass to be colonized by humans.
Most of its endemic animals descended from taxa that colonized it during the
late Mesozoic or early Cenozoic when it was still relatively close to larger landmasses. 
In later Cenozoic times, volant birds from Australia periodically flew here and 
radiated into new endemics.

Genetic evidence suggests that the 9 Holocene species of moa radiated from a common ancestor during the late Miocene with the Upland Moa (Megalapteryx didinus), the sole member of the family Megalapterygidae, being the most basal. The two species of Dinornis within the family Dinornithidae were the largest and tallest of the moa very slender skeletons and elongated limbs adapted for mobility. The family Emeidae is the most diverse, containing the remaining 6 species within 4 genera: 3 species within Pachyornis and the genera Anomalopteryx, Euryapteryx, and Emeus containing a single species each. Contained within this family are the smallest, as well as some of the most heavily-built moa.

• Megalapterygidae
• Upland Moa (Megalapteryx didinus)
•  
• Dinornithidae
• North Island Giant Moa (Dinornis novaezelandiae)
• South Island Giant Moa (Dinornis robustus)
•  
• Emeidae
• Bush Moa (Anomalopteryx didiformis)
• Coastal Moa (Euryapteryx curtus)
• Eastern Moa (Emeus crassus)
• Heavy-footed Moa (Pachyornis elephantopus)
• Mantell’s Moa (Pachyornis geranoides)
• Crested Moa (Pachyornis australis)

Reconstructed skulls of the 9 species of moa shown to scale, alongside
silhouettes of each species. Restored skulls are drawn from specimens from 
the online collections of Museum of  New Zealand Te Papa Tongarewa. 
Scale bar in lower left corner equals 3cm.

Part 2: Anatomy & Action

Part 3: Paleoecology

Part 4: Behavior

Part 5: Extinction

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>

Allentofta ME, Hellerd R, Oskamb CL, Lorenzena ED, Halec ML, Gilberta TP, Jacombg C, Holdawayc RN, Bunce M (2014). "Extinct New Zealand megafauna were not in decline before human colonization". PNAS 111(13): 4922–4927 <Full Article>

Brassey CA, Holdaway RN, Packham AG, Anne´ J, Manning PL, Sellers WI (2013). "More than one way of being a moa: differences in leg bone robustness map divergent evolutionary trajectories in Dinornithidae and Emeidae (Dinornithiformes)". PLoS ONE 8(12): e82668. doi:10.1371/journal.pone.0082668 <Full Article>

Hand SJ, Worthy TH, Archer M, Worthy JP; Tennyson AJD, Scofield RP (2013). "Miocene mystacinids (Chiroptera, Noctilionoidea) indicate a long history for endemic bats in New Zealand". Journal of Vertebrate Paleontology 33(6): 1442-1448 <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>

Morten A, Rawlence N (2012). “Moa’s ark or Volant ghosts of Gondwana? Insights of nineteen years of ancient DNA research on extinct moa (Aves: Dinornithiformes) of New Zealand”. Animals of Anatomy 194: 36-51 <Full Article>

Worthy TH (2011). "Terrestrial turtle fossils from New Zealand refloat Moa's Ark". Copeia 1: 72-76 <Full Article>

Tennyson AJD, Worthy TH, Jones CM, Scofield RP, Hand SJ (2010). "Moa’s Ark: Miocene fossils reveal the great antiquity of moa (Aves: Dinornithiformes) in Zealandia". Records of the Australian Museum 62: 105–114 <Full Article>

Buncea M, Worthy TH, Phillips MJ, Holdaway RN, Willerslev E, Hailef J, Shapiro B, Scofieldi RP. Drummond A, Kamp PJJ, Cooper A (2009). "The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography". Proceedings of the National Academy of Science 106(49): 20646–20651 <Full Article>

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>