Moas
| Moas | ||||||||||
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Two moas are attacked by a Haastadler |
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| Bonaparte , 1853 |
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The moas (singular: the moa) (Dinornithiformes) were flightless, now extinct representatives of ratites . In historical times they were distributed with nine species over both islands of New Zealand .
features
As ancient jawbones (Palaeognathae), moas had a palaeognathic palate , which means that, in contrast to the so-called new - jaw birds , they show a pterygoid-palatine complex (PPC), which consists of the cranial bones wingbones (pterygoid), palatine bones (palatinum) and ploughshare bones (vomer ) consists. They resembled other ratites in a number of anatomical features: their upper and lower jaws each ended in a three-part horned beak ( Rhamphotheca ), the middle crest of which was flat and separated from the beak's lateral parts by furrows. The nasal process of the intermaxillary bone was unpaired and not fused with the nasal . In the pelvic girdle , the window between the iliac and the ischium ( foramen ilioischiadicum ) was elongated and not closed at the back. The broad and flat sternum showed no signs of a sternum keel ( Carina sterni ).
The order of the moas (Dinornithiformes) is defined by the following derived characteristics of the skeleton , in which moas differ from other ratites : Wings were completely absent. From the shoulder girdle there was only a stunted scapulo coracoid with no signs of a shoulder joint socket . The pelvis was wide in and behind the acetabulum . The sternum showed well defined lateral processes. The end of the shin near the foot was equipped with a tendon canal that was bridged by a bony connection. The walking leg had two hypotarsal ridges instead of one. Moas had 21 to 23 cervical vertebrae , 6 thoracic vertebrae , 18 pelvic vertebrae and 11 caudal vertebrae , the last caudal vertebrae not being fused into a pygostyle . A number of skull features add to the characteristics mentioned.
Most species of moa were short-legged and the size of a turkey . In contrast, the females of the two species of the genus Dinornis were the largest birds in New Zealand. Their weight was about 180 kilograms, according to other estimates up to 270 kilograms. They kept their heads stretched forward and level with their backs or below; this was due to the shape of the spine , which curved downwards in front of the thoracic vertebrae , with the lowest point between vertebrae 12 and 16 (counted from the skull); the front cervical vertebrae were so short that they hardly contributed to the elevation of the head. Thus, the largest representatives of the moas, which were shown in older reconstructions with an upright neck and would have been taller than an African ostrich , had a head height of barely more than two meters.
The largest known specimens of eggs of the moas were 40 centimeters high and weighed around 4500 grams, so their content corresponded to that of more than 80 average chicken eggs.
distribution and habitat
The moas originally had some misunderstandings about their habitat. They were compared with large ratites such as ostriches and rheas living today and deduced from this that they must have been birds of the open area. The geologist Julius von Haast , who was the first to deal intensively with these birds, described moas as birds of the savannah and the edge of the forest, which hardly ever penetrated the forest. This theory remained popular until the 1950s. Only then did palynology show that, with the exception of the subalpine zones , New Zealand was completely forested before the arrival of the Māori , so the grasslands were by no means a natural landscape. In addition, the examination of stomach contents showed that all species ate the buds, leaves and fruits of forest plants.
Moas lived on the North and South Island of New Zealand. Two species were found exclusively on the North Island, five only on the South Island; the other two species were found on both islands. Only one type of Dinornis was found on Stewart Island .
Way of life
Moas were exclusively herbivores. By examining the gizzards of particularly well-preserved moa fossils, it was found that Dinornis apparently mainly grazed branches, while Emeus and Euryapteryx ate softer foods such as leaves and fruits. No stomach contents are known from representatives of other genera, but stomach stones ( gastroliths ) up to five centimeters in size . There is no evidence for a proportion of animal food.
Moas laid one or two eggs per clutch. About thirty preserved moa eggs and countless shell remains have been found so far. In the rarest of cases, however, it was possible to assign the eggs to a species. In one case, the remains of a likely brooding moa and egg were found, which made the assignment easy. In other cases, comparisons of the frequency of moa and egg fossils in certain regions were used to conclude that they belonged together. It is noticeable that moa eggs are unusually large. The egg of a Euryapteryx curtus , a moa weighing only 20 kilograms, was as big as that of the much larger emus . The eggs of the female Dinornis , the largest of all moas, were with dimensions of 24 × 18 cm and volumes of about 4300 cm 3 significantly larger than an ostrich egg and about 90 times as large as a medium-sized hen egg. The size of the eggs allows the conclusion that the newly hatched young moas were highly developed and to a large extent independent.
The sounds made by Moas could also be clarified by examining a mummified Euryapteryx . In this case, the windpipe forms a 1.20 meter long loop, a structure similar to that found in the trumpeter swan. Such an organ enabled the bird to produce very loud and long-range calls. Whether other Moa genera had comparable devices is still speculation at the moment.
Before the arrival of humans, the Haastadler was the only enemy of the Moas. For him, the main prey was mainly the small and medium-sized species. But the giant females of the two Dinornis species also fell victim to the gigantic bird of prey. This is known from the examination of the remains of various moas that show signs of severe pelvic injury . They suggest that the eagle attacked its prey from behind. The pelvic bones were literally pierced by the eagle's claws.
Growth, Ontogeny, and Population Structure
Compared to all other bird groups, including other ratites , moas, as extreme K-strategists , showed a long growth time and a very late achievement of sexual maturity . In histological examinations of the cortical tissue of various leg bones ( thighbones , tibiotarsus , tarsometatarsus ), Turvey u. a. (2005 ) demonstrated a clear zoning of the outer bony cortex and several seasonal growth pauses, so-called LAGs ( English : Lines of Arrested Growth , "annual rings") in four of the six known genera . They show that the individuals concerned only reached their final size after several years of discontinuous growth.
The giant moas of the genus Dinornis deviated from this scheme. As a result of a pronounced sexual dimorphism , the females, previously wrongly classified as a separate species Dinornis giganteus , weighed over 200 kilograms, while the males weighed up to 85 kilograms (Bunce et al. 2003, Huynen et al. 2003). In order to achieve these body sizes, the growth of the representatives of the genus Dinornis was apparently accelerated compared to that of other Moa genera: Their outer bone cortical tissue (corticalis) is permeated by many blood vessels , shows hardly any zoning and only has LAGs in a few cases. Apparently the Dinornis species were fully grown after about three years, while some of the smaller moas such as Euryapteryx took up to nine years for this.
In order to elucidate the age structure of moa populations , the moa bones of various fossil sites were systematically investigated (Turvey and Holdaway (2005)): It turned out for the site Bell Hill Vineyard Swamp (near Waikari, North Canterbury on the South Island) that only a good quarter (27.5%) of the Dinornis robustus bones collected there belonged to non-adult animals, while the remainder came from adult, mostly sexually mature individuals. Similar to the recent kiwifruit , the metatarsal bones of some of the adult animals were not completely fused, which suggests that they were not yet sexually mature. The noticeably low proportion of fossilized young animals could indicate that a very high proportion of the offspring reached adulthood. This interpretation is only correct, however, if the present grave community represents the conditions of an actual population .
Turvey et al. a. interpret the slow growth rates and delay in sexual maturity in moas as a result of adaptation to habitats devoid of predatory mammals . The very low rate of reproduction was responsible for the fact that human persecution led to its rapid extinction before other factors such as habitat loss had a negative impact.
Another rich site of moa fossils is the Pyramid Valley , also in North Canterbury .
Moas and humans
The extermination
It is noticeable that moas do not appear in the myths and legends of the Māori tribes . It could therefore be assumed that they were extinct so long ago that the existence of the giant birds had been forgotten over the generations.
The history of the extermination can now be reconstructed quite well. At the end of the 13th century, Polynesian immigrants reached New Zealand, which was probably previously deserted, and began to clear the closed forests. Early Polynesian settlement sites contained large amounts of moa bones. With the exception of Pachyornis australis , remains of every Moa species have been found associated with humans. The moas had no natural enemies apart from the Haastadler . In general, a lack of escape or defense behavior can be observed in birds that live on predator-free islands. The appearance of human hunters probably triggered neither flight nor resistance among the moas. Worthy and Holdaway speculate that the moa hunt was more like "shopping in the supermarket" than a hunt.
Even the Polynesian remains from the second half of the 14th century no longer show any Moa bones. This suggests an extremely short period of extinction. The original population of New Zealand is now estimated at 200 people. Holdaway and Jacomb made an attempt in 2000 to reconstruct the extinction of the moas and came up with extremely short periods of time for some regions; they made a period of only five years plausible for the extinction of all native moa species on the Coromandel Peninsula .
The extinction of the moas was so rapid that the Māori did not even have to develop weapons that specialized in moa hunting. By the end of the 14th century, moas were extinct. It is conceivable that individual specimens survived longer in particularly remote regions. But when James Cook anchored off New Zealand in 1769, the last of the moas must have long since disappeared.
Today there are some followers of cryptozoology who look for living moas , especially in the fjord country . Often there are also reports from hikers who claim to have seen moas; occasionally these reports are backed up with blurry photos. Scientists believe that the moas' survival is completely out of the question.
The rediscovery
Since the moas had disappeared from the tradition of the Māori, they were only rediscovered on the basis of fossil finds. Who found the first bone of a moa is no longer reliably traceable today. In 1838 the trader Joel Samuel Pollack reported bone finds that Māori had drawn attention to and from which he concluded that emus or ostriches were once native to New Zealand. Other travelers made similar discoveries almost simultaneously.
The zoologist and paleontologist Richard Owen (1804-1892) dedicated himself to the moas in a special way . In 1840 he published the first publication on the previously unknown large birds ( On the bone of an unknown struthious bird from New Zealand ) in which he came to the following conclusion: “I am willing to risk my reputation for the conclusion that it In New Zealand there were or are still ostrich-like birds that were close to or equal in size to today's ostrich. ”Owen described most of the moa species known today and published almost 50 other articles on moas over the course of the next fifty years.
The German-born naturalist Julius von Haast made other major contributions to moa research, who built up a collection of moa fossils and, in addition to making merit in describing other species, speculated about the way of life of the moas. Although many of his assumptions have now been refuted, they are often found quoted. The hypothesis, which is now considered improbable, goes back to Haast that it was not the Māori who exterminated the moas, but a people who previously lived in New Zealand and which he called the "moa hunters".
The word “moa” simply means hen in many Polynesian languages . The application of this name to the giant birds probably goes back to the missionary William Colenso , who, after visiting the Māori in Waiapu, related a myth that the locals believed in. This reports of a gigantic chicken with the face of a human being, which was guarded by two giant lizards and trample every intruder to death. This being would be called a moa. Due to similar legends, the Māori words Tarepo and Te Kura were also initially related to the giant birds. Ultimately, the term moa prevailed.
Systematics
The following system is based on Bunce et al. (2009). In their work, the moas form three different families.
- Order Dinornithiformes
- Family Dinornithidae
- Genus Dinornis
- D. novaezealandiae , North Island
- D. robustus , South Island
- Genus Dinornis
- Family Emeidae
- Genus Anomalopteryx
- A. didiformis , North and South Island
- Genus Emeus
- Lesser moa , E. crassus , eastern South Island
- Genus Euryapteryx
- Coastal Moa , E. curtus , North and South Island lowlands
- Genus Pachyornis
- Elephant foot moa , P. elephantopus , eastern South Island
- P. australis , high altitudes of the South Island
- P. mappini , North Island
- Genus Anomalopteryx
- Family Megalapterygidae
- Genus Megalapteryx
- Forest moa , M. didinus , altitudes of the South Island (> 900 m)
- Genus Megalapteryx
- Family Dinornithidae
The following cladogram , based on comparisons of DNA sequences , shows the internal relationship of the Dinornithiformes:
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The systematic position of the moas to other bird groups is unclear. Since there is another order of ratites in New Zealand, the kiwis, the classic view is to regard both taxa as closely related. This classification is still favored by some experts today. Lee et al. a. (1997) Kiwis and Moas as sister groups next to each other based on morphological analyzes . On the other hand, Cooper (1997, 2001), based on DNA analyzes, comes to the conclusion that Moas as a sister group should be compared to a common taxon of ostriches, cassowaries , emus and kiwis; all together are in turn sister group of the rheas. Recently published works, however, see the moas as a sister group of the flighty cockatiels (Tinamiformes).
Fossil record
The oldest finding of a moa in the fossil record is Anomalopteryx from the late Pliocene about 2.5 million years ago. 33 Moas fossil remains are known from the Pleistocene . Finds from deposits before the Holocene are therefore very rare, but this applies to the fossil record on the New Zealand islands as a whole. All moa fossils found so far can be assigned to the species known from the Holocene. Accordingly, no Moa species became extinct or emerged during the Pleistocene, but lived on almost unchanged until they were almost simultaneously exterminated by humans. Often there is only a slight decrease in size between the Pleistocene and the Holocene.
Even if there is no corresponding fossil evidence, the moas are a much older group of animals than their fossil record has so far documented. No fossils of the ancestors of the moas have yet been found.
See also
literature
- Alan Feduccia : The Origin and Evolution of Birds. Yale University Press, London-New Haven 2 1999, ISBN 0-300-07861-7 .
- L. Huynen et al .: Nuclear DNA sequences detect species limits in ancient moa. In: Nature 425, 2003, pp. 175-178. doi : 10.1038 / nature01838
- Richard Owen: On the bone of an unknown struthious bird from New Zealand. In: Proceedings of the Zoological Society of London for 1839. Part VII, No. lxxxiii. London 1840, 169-171. ISSN 0370-2774
- Samuel T. Turvey , et al .: Cortical growth marks reveal extended juvenile development in the New Zealand moa . In: Nature 435, 2005, pp. 940-943. doi : 10.1038 / nature03635
- Samuel T. Turvey & Richard N. Holdaway: Postnatal Ontogeny, Population Structure, and the Extinction of the Giant Moa Dinornis . In: Journal of Morphology 256, 2005, pp. 70-86. ISSN 1097-4687
- Trevor H. Worthy , Richard N. Holdaway: The Lost World of the Moa. Prehistoric Life of New Zealand. Indiana University Press, Bloomington 2002, ISBN 0-253-34034-9 .
Web links
- The moa. Blog: Critically Endangered ?, archived from the original on January 17, 2012 ; Retrieved November 22, 2015 (original website no longer available).
- Not only big, but also many. On: Wissenschaft.de of November 10, 2004. About a study in Biology Letters (Volume 271, 2004, doi: 10.1098 / rsbl.2004.0234 ).
Individual evidence
- ↑ a b c M. Bunce, TH Worthy, MJ Phillips, RN Holdaway, E. Willerslev, J. Haile, B. Shapiro, RP Scofield, A. Drummond, PJJ Kamp & A. Cooper. The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography. Proceedings of the National Academy of Sciences , 2009; DOI: 10.1073 / pnas.0906660106
- ↑ Berliner Zeitung of July 12, 2011, page 12
- ↑ Michael Bunce et al .: Extreme reversed sexual size dimorphism in the extinct New Zealand moa "Dinornis" . In: Nature 425, 2003, pp. 172-175. doi : 10.1038 / nature01871
- ↑ Spectrum : Extinction - only a few people are enough from November 7, 2014, loaded on January 23, 2017
- ^ R. Holdaway & C. Jacomb: Rapid extinction of the moas (Aves, Dinornithiformes). Model, test and implications. In: Science 287, 2000, pp. 2250-2254. doi : 10.1126 / science.287.5461.2250
- ↑ K. Lee, J. Feinstein, J. Cracraft: The phylogeny of ratite birds. In: D. Mindell (Ed.): Avian Molecular Evolution and Systematics. Academic Press, New York 1997, pp. 173-211. ISBN 0-12-498315-4
- ^ Alan Cooper: Ancient DNA and avian systematics. From Jurassic Park to modern island extinctions . In: D. Mindell (Ed.): Avian Molecular Evolution and Systematics. Academic Press, New York 1997, pp. 173-211. ISBN 0-12-498315-4
- ↑ Alan Cooper et al .: Complete mitochondrial genome sequences of two extinct moas clarify ratite evolution . In: Nature 409, 2001, pp. 704-707. doi : 10.1038 / 35055536
- ↑ Kieren J. Mitchell, Bastien Llamas, Julien Soubrier, Nicolas J. Rawlence, Trevor H. Worthy, Jamie Wood, Michael SY Lee, Alan Cooper: Ancient DNA reveals Elephant Birds and Kiwi are Sister Taxa and Clarifies Ratite Bird Evolution. In: Science . Volume 344, 2014, pp. 898-900, doi: 10.1126 / science.1251981 .
- ↑ Takahiro Yonezawa, Takahiro Segawa, Hiroshi Mori, Paula F. Campos, Yuichi Hongoh, Hideki Endo, Ayumi Akiyoshi, Naoki Kohno, Shin Nishida, Jiaqi Wu, Haofei Jin, Jun Adachi, Hirohisa Kishino, Keny Kurokawa, Yoshifif Nogi, Hide , Harutaka Mukoyama, Kunio Yoshida, Armand Rasoamiaramanana, Satoshi Yamagishi, Yoshihiro Hayashi, Akira Yoshida, Hiroko Koike, Fumihito Akishinonomiya, Eske Willerslev, Masami Hasegawa: Phylogenomics and Morphology of Extinct Paleognaths Reveal the Origin. In: Current Biology Volume 27, 2017, pp. 68-77, doi: 10.1016 / j.cub.2016.10.029 .
