Systematic revision of the living African Slender-snouted Crocodiles (Mecistops Gray, 1844).

ZOOTAXA 4504(2): 151-193. 24 Oct. 2018. DOI: 10.11646/zootaxa.4504.2.1.

Abstract:

Molecular and morphological evidence has shown that the African slender-snouted, or sharp-nosed, crocodile Mecistops cataphractus (Cuvier, 1824) is comprised of two superficially cryptic species: one endemic to West Africa and the other endemic to Central Africa. Our ability to characterize the two species is compromised by the complicated taxonomic history of the lineage and overlapping ranges of variation in distinguishing morphological features. The name M. cataphractus was evidently originally based on West African material, but the holotype is now lost. Although types exist for other names based on the West African form, the name M. cataphractus is sufficiently entrenched in the literature, and other names sufficiently obscure, to justify retypification. Here, we designate a neotype for M. cataphractus and restrict it to West Africa. We resurrect M. leptorhynchus as a valid species from Central Africa and identify exemplary referred specimens that, collectively, overcome the obscurity and diagnostic limits of the extant holotype. We additionally indicate suitable neotype material in the event the holotype is lost, destroyed, or otherwise needing replacement, and we rectify the previously erroneous type locality designation. We provide a revised diagnosis for crown Mecistops, and revise and update previous descriptions of the two living species, including providing both more complete descriptions and discussion of diagnostic characters. Finally, we provide considerable discussion of the current state of knowledge of these species’ ecology, natural history, and distribution.

shirley-biblio

Divergent Morphology among Populations of the New Guinea Crocodile, Crocodylus novaeguineae (Schmidt, 1928): Diagnosis of An Independent Lineage and Description of A New Species.

Copeia. 107(3): 517-523.

Abstract:

The New Guinea Crocodile (Crocodylus novaeguineae) is a freshwater species of crocodilian endemic to the island of New Guinea in northern Oceania. The species inhabits both the country of Papua New Guinea in the east and Indonesian West Papua. Crocodylus novaeguineae occurs on both the northern and southern side of the Central Highlands, which span east to west dividing the entire island into northern and southern halves. Like most crocodilians, C. novaeguineae inhabits various grassy and forested swamps in lowland freshwater areas and has maintained both cultural and economic significance in the region for centuries. Neill (1971) and, more recently, Hall (1989) have suggested that Crocodylus novaeguineae on the northern side of the Central Highlands (“NCN”) and those on the southern side (“SCN”) are on independent evolutionary trajectories and should be taxonomically recognized. Hall (1989) attempted to affirm the suspicions of Neill and presented compelling morphological and ecological data to do so. Morphologically, the northern and southern hypothesized lineages differed in proportional premaxillary (PXS) to maxillary (MXS) length (NCN: MXS > PXS; SCN: PXS > MXS) and patterns of cervical squamation (NCN: >4 post-occipital scutes with lateral contiguity between them, anteromedial nuchal scute separation absent; SCN: 4 post-occipital scutes with lateral discontinuity between them, anteromedial nuchal scute separation present). Ecologically, C. novaeguineae south of the Central Highlands nest in the wet season, in synchrony with sympatric Crocodylus porosus, whereas north of the Central Highlands, nesting occurs in the dry season. Additionally, variation in reproductive strategy (clutch size and egg size ratios) was diagnosed between NCN and SCN; however, reproductive strategy is highly plastic, even intraspecifically, among crocodilians. Thus, these character states are not robustly interpretable as diagnostic. Phylogenetic approaches using molecular data were later tested and interpreted in the unpublished thesis of Gratten (2003) in which NCN and SCN were considered distinct operational taxonomic units in light of Hall (1989). A Bayesian analysis of relationships of Indo-Pacific Crocodylus using mtDNA curiously recovered a paraphyletic C. novaeguineae, rendered so by the purported Borneo Crocodile C. raninus, described from a skull and two preserved juveniles with no known extant population (Muller and Schlegel, 1844). NCN was recovered as more closely related to C. raninus than to SCN. This finding was attributed to either extremely recent divergence in NCN or misidentification of a dispersed or introduced NCN to Borneo from which the molecular sample was taken. Oaks (2011) recovered a paraphyletic C. novaeguineae; however, all samples of this species were from captive animals and identification of some samples appeared problematic. Thus, our analyses and comparisons herein only include populations of C. novaeguineae due to the lack of biologically reasonable comparisons. Crocodylus novaeguineae is the only freshwater crocodilian in the region besides the putative C. raninus. Little material with robust locality data exists in collections for this species, and in the absence of more specimens and diverse datasets we are unable to make additional comparisons. An improved analysis of morphological variation among populations of C. novaeguineae is warranted, given the ecological and molecular patterns that have slowly emerged. Here, we use multivariate geometric morphometric approaches to gain clarity on the differentiation of populations north and south of the Central Highlands by assessing cranial shape variation across the distribution. We aim to identify diagnostic characters for populations on independent evolutionary trajectories and test whether cranial shape variation corresponds to the hypothesized lineages (a clade north of the central highlands and one south). We predicted that specimens from drainages on the northern side would more closely resemble each other than specimens from drainages on the southern side of the highlands and that shape-based diagnostic characters would be revealed.

murray-biblio

Krokodile: Alligatoren, Kaimane, echte Krokodile und Gaviale.

Die Neue Brehm Bücherei Bd. 593.
Westarp Wissenschaften Magdeburg. isbn 3-89432-420-1

Verlagstext:

Nur wenige Menschen wissen, daß die heute noch lebenden Krokodile enger mit den ausgestorbenen Dinosauriern oder den Vögeln verwandt sind als mit anderen Reptiliengruppen. Ihre isolierte Stellung ist durch viele Besonderheiten in der Biologie gekennzeichnet. Von den 22 noch lebenden Krokodilarten sind 21 in ihrer Existenz bedroht*. Die Verwendung ihrer Häute als überflüssige Lederwaren, die Zerstörung der Lebensräume und die Jagd auf sie als vermeintlich gefährliche Konkurrenten um Nahrung und Raum haben zu dieser dramatischen Situation geführt. Auf der anderen Seite werden Farmen errichtet, um die kommerziellen Interessen zu steuern und die Wildbestände zu schonen. Der Verfasser greift diese Themenvielfalt auf. Er beschreibt in einem allgemeinen Teil auf der Grundlage der Biologie der Tiere diese Gegensätze und behandelt auch Fragen zu Haltung und Nachzucht. In einem speziellen Teil werden alle Arten mit Abbildungen und Verbreitungskarten vorgestellt. Angaben zu Färbung und Aussehen, Verbreitung und Lebensraum sowie zur Ökologie runden diese Besprechungen ab.

* NB: Das trifft heute nicht mehr zu!

Mugger Crocodile - Crocodylus palustris.

In: Crocodiles.Status Survey and Conservation Action Plan: 94-98.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

The  mugger is a hole-nesting species, with egg-laying taking place during the annual dry season. Females become sexually mature at approximately 1.8-2 m, and lay 25-30 eggs. Nests are located in a wide variety of habitats, and females have even been known to nest at the opening of, or inside, their burrow. In captivity, some Muggers are known to lay two clutches in a single year, but this has not been observed in the wild. Incubation is relatively short, typically lasting 55-75 days. Like a number of other crocodilians, C. palustris is known to dig burrows. Whitaker and Whitaker (1984) referred to mugger burrows in Sri Lanka and India (Gujarat and South India) and noted that yearling, sub-adult and adult mugger all dig burrows. In Iran they are sometimes known to dig two burrows close to each other, which may be used by one or  more  crocodiles  (Mobaraki  2002).  These  burrows  are presumably utilized as an effective refuge from hot daytime ambient temperatures. These burrows play a critical role in the survival of crocodiles living in harsh environments, allowing them to avoid exposure to excessively low and high temperatures (<5ºC and >38ºC respectively) for long periods of time, which may be lethal. Mugger are known to undertake long-distance overland treks.

Nile Crocodile - Crocodylus niloticus.

In: Crocodiles.Status Survey and Conservation Action Plan: 84-89.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

More than 750 surveys using a variety of methods have been carried out for C. niloticus since the 1950s. Despite covering 315 different locations only  8  of  these  have  been  surveyed  enough  to  allow estimation of population trends. All of these are located in southern and East Africa where there have been significant recent improvements in monitoring. In central and West Africa the availability of survey data is very poor. Overall, survey data are insufficient or non-existent in 25 of 42 Range States. The need for wild population recovery and/or conservation is moderate throughout much of east and southern Africa with recent  detailed  studies suggesting an urgent need for conservation action in specific areas, but is high in central and West Africa. Many populations are believed  to  have  recovered by the 1990s but are now constrained or in decline due to anthropogenic factors.

Breeding Morelet's crocodile at Atlanta Zoo.

International Zoo Yearbook, 13:103-105.

Einleitung:

In 1971, for the first time in captivity, we observed our Morelet's crocodiles Crocodylus moreletii establishing territories, mating, building nest mounds, laying viable eggs and assisting their young from the nest. Our colony was obtained in July 1965 in the Mexican state of Yucatan as juveniles.

American Crocodile - Crocodylus acutus.

In: Crocodiles.Status Survey and Conservation Action Plan: 46-52.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin

Aus dem Inhalt:

The American crocodile is the most widely distributed of the New World crocodiles, ranging from the southern tip of Florida, along both the Atlantic and Pacifi c coasts of southern Mexico, Central America, and northern South America, as well
as the Caribbean islands of Cuba, Jamaica, and Hispaniola. The habitat of C.  acutus consists largely of brackish water coastal habitats such as the saltwater sections of rivers, coastal lagoons, and mangrove swamps. However, populations are
known from freshwater areas located well inland, including a number of reservoirs. A signifi cant population is known from Lago Enriquillo, a landlocked hypersaline lake situated 40 m below sea level in the arid southwestern Dominican Republic.

New Guinea Freshwater Crocodile - Crocodylus novaeguineae.

In: Crocodiles.Status Survey and Conservation Action Plan: 71-78.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

In Papua New Guinea, recognition of unregulated hunting taking  place  led  the  Department  of  Environment  and Conservation (DEC) to: introduce legislative controls in the late 1960s; and, and establish a regulated program in the 1970s based on cropping and ranching. Crocodiles are managed at sustainable levels for the benefi t of customary landowners who own most of the land in Papua New Guinea. Crocodiles can  be  legally  harvested  by  landowners  for  personal use (food and ritual), but commercial sale and export of hides is restricted to the size range of 18-51 cm belly width, which corresponds to approximately 0.9-2.1 m total length.

Wild harvests declined from over 20,000/year in 1977-1980 to 12,000-20,000/year in 1981-1989, then fl uctuated between 10,000-20,000/year  (1997-2005)  (Solmu  and  Sine  2009). Until  the  mid-1990s  hatchlings  and  eggs  were  collected and raised in centralized ranches. Harvests for this purpose ranged  from  2500  to  10,000.  Early  attempts  to  establish village level ranches fl oundered due to technical limitations, particularly feed (locally caught fi sh), water and management defi ciencies. Trade in live juveniles and eggs to centralized raising facilities continued until 1995 when the largest farm halted purchases of the species due to market prospects and its Saltwater crocodile-oriented management strategy.

Morelet’s Crocodile - Crocodylus moreletii.

In: Crocodiles.Status Survey and Conservation Action Plan: 79-83.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin

Aus dem Inhalt:

Morelet’s crocodile is a medium-sized species (males to 4.5 m) occurring in the Atlantic lowlands of the Gulf of Mexico (Mexico) and the Yucatan Peninsula (Mexico, Belize and Guatemala). Knowledge of this species has increased rapidly over the past two decades, and recently a great deal of research has been conducted on its distribution and status in Mexico and Belize, nesting ecology, diet and foraging ecology, morphometrics, population ecology and ecotoxicology.

platt-biblio

Australian Freshwater Crocodile - Crocodylus johnstoni.

In: Crocodiles.Status Survey and Conservation Action Plan: 66-70.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

Aus dem Inhalt:

The Australian Freshwater Crocodile was formally described as Crocodylus johnsoni intended to name the species after Mr. Robert Johnstone, but mispelt the name as “Johnson”. Cogger et  al. (1983) reviewed the nomenclature and reinstated the name Crocodylus johnstoni, which is the name most commonly applied in the scientific and general literature, and in Australian State/Territory and Federal legislation. This correction was unnoticed by some (King  and  Burke 1989), so “Crocodylus johnsoni” still appears in some contexts (CITES and IUCN).