Osteological and historical data on extinct island night herons (1 Viewer)

[Fred Ruhe]

Julian P. Hume, 2024

Osteological and historical data on extinct island night herons (Aves: Ardeidae), with special reference to Ascension Island, the Mascarenes and Bonin Islands

Geobios, Volume 83, April 2024, Pages 21-38

Abstract and free pdf: https://www.sciencedirect.com/scien...?ref=pdf_download&fr=RR-2&rr=8a17a09e29f89fdc

Night herons of the genus Nycticorax and Nyctanassa are adept island colonisers, occurring on a number of oceanic islands and island archipelagos. Continental species and those inhabiting large islands are generally not considered threatened, whereas night herons restricted to small, oceanic islands are particularly vulnerable to human interference. As a result, six out of nine described species and one subspecies, all derived from Nycticorax nycticorax, Nycticorax caledonicus or Nyctanassa violacea, are now extinct whereas a further three extinct species await description. The extinct island endemics generally exhibit morphological adaptations to an insular environment and diet, such as an increase or decrease in size, robust jaws and legs, and smaller wings with associated reduced flying ability than founding stock. Here I present an osteological comparison along with historical descriptions of the extinct, oceanic island night herons, with special reference to the Mascarene and Ascension fossil species, and Bonin Island subspecies, and show the degree of morphological changes between the founding and island taxa. I further discuss the reasons why they became extinct.

Enoy,

Fred

 

[Fred Ruhe]

Systematic palaeontology

Class Aves Linnaeus, 1758
Order Pelecaniformes Sharpe, 1891
Family Ardeidae Leach, 1820
Genus Nycticorax T. Forster, 1817
Ascension Night Heron Nycticorax olsoni Bourne, Ashmole and
Simmons, 2003
Figs. 1–5
1977. Nycticorax sp. - Olson, p. 41 (Site 4, Ascension).
2003. Nycticorax olsoni - Bourne et al., p. 46 (Chapel Grotto,
Ascension

Distribution: Ascension, South Atlantic.


Fig. 1. Comparison of coracoid (ventral aspect, left) and scapula (left lateral surface) of Nycticorax nycticorax with N. olsoni. A, B. Coracoid. A: N. nycticorax (NHMUK S/ 1988.67.1 F); B: N. olsoni (USNM 209515). C, D. Scapula. C: N. nycticorax (NHMUK S/ 1988.67.1 F); D: N. olsoni (NHMUK S/1999.1.1). Scale bar: 10 mm.


Fig. 2. Comparison of humerus (left) and ulna (right, ventral aspect) of Nycticorax n. nycticorax with N. olsoni. A-D. Humerus (left side). A, C: N. n. nycticorax (NHMUK S/ 1988.67.1 F), caudal (A) and cranial (C) surface; B, D: N. olsoni (NHMUK S/1999.1.1), caudal (B) and cranial (D) surface. E, F. Ulna. E: N. olsoni (NHMUK S/1999.1.1); F: N. n. nycticorax (NHMUK S/1988.67.1 F). Scale bar: 10 mm.


Fig. 3. Comparison of carpometacarpus (ventral aspect, right) and phalanx digiti majoris (left ventral aspect) of Nycticorax n.ycticorax with N. olsoni. A, Carpometacarpus. A: N. n. nycticorax (NHMUK S/1988.67.1 F); B: N. olsoni (NHMUK S/1999.1.1). C, D. Phalanx digiti majoris. C: N. olsoni (NHMUK S/1999.1.1); D: N. n. nycticorax (NHMUK S/1988.67.1 F). Scale bar: 10 mm.