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Holohalaelurus Fowler
No full text[[Genus Holohalaelurus Fowler]] The genus Holohalaelurus is an obscure group of catsharks endemic to deeper waters off southern and eastern Africa, and range from the temperate southeastern Atlantic Ocean, into the tropical western Indian Ocean. Prior to this revision, it was commonly accepted that there were two valid species of Holohalaelurus, H. punctatus (Gilchrist 1914) and H. regani (Gilchrist 1922), two synonyms, H. polystigma (Regan 1921) and H. melanostigma Norman 1939, and that a species complex involving both of the valid species existed in the tropical west Indian Ocean. The literature referring to Holohalaelurus is largely restricted to taxonomic descriptions of Holohalaelurus species, and basic revisions as part of larger scale works at the familial, ordinal, or class level. The exception to this is the literature available for H. regani, which is an abundant species, endemic to southern Africa, and regularly caught in demersal fishing trawls off South Africa and Namibia (Compagno & Smale, 1989; Compagno et al., 1991; Richardson et al., 2000). Original descriptions of all the nominal species of Holohalaelurus are brief and insufficient to discriminate between the species due to the morphological conservation within the genus. The lack of detailed species descriptions, and species complexes referred to in the literature occurring along the east coast of Africa, made a revision of this genus necessary. This account is the first revisionary work dedicated to the genus Holohalaelurus.Published as part of Brett A. Human, 2006, A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species., pp. 1-56 in Zootaxa 1315 on page
Poroderma Smith
No full text<p>[[Genus Poroderma Smith]]</p> <p>There is a minor directed fishery for Poroderma sharks for the aquarium trade; however, they are a significant bycatch in many fisheries including both recreational and commercial linefishing, and demersal trawling (Bass et al. 1975; Buxton et al. 1984; Guastella 1993; Pradervand 1999; pers. obs.). These sharks also suffer from persecution from the commercial linefishery, as illustrated by Smith (1949: 53), who describes P. africanum as “…a pest to anglers”, particularly in the commercial linefishery, where the fisherman perceive these sharks to be ‘stealing’ their bait and make a point of killing the shark before discarding it. Bycatch mortality can be considered to be close to 100% in those fisheries where persecution exists (pers. obs.); therefore, fishery pressure for these species is grossly underestimated.</p> <p>Although P. africanum is readily recognisable, colour pattern variation in P. pantherinum has caused taxonomic confusion in the past, and it appears that there may be ontogenetic and geographic factors that are partly responsible for that variation. In this study, the taxonomy of species of Poroderma is assessed, the first detailed description of the colour pattern variations in P. pantherinum, and a novel identification key for the genus, are provided. Taxonomic resolution of this genus will allow better fisheries management for these sharks.</p>Published as part of <i>Brett A. Human, 2006, A taxonomic revision of the catshark genus Poroderma Smith, 1837 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)., pp. 1-32 in Zootaxa 1229</i> on page
Poroderma Smith 1837
No full textPoroderma Smith, 1837 Poroderma Smith, 1837: 85. Conoporoderma Fowler, 1934: 234 (as a subgenus of Poroderma); Bigelow and Schroeder 1948: 197 (replacement for Poroderma). Type Species. Squalus africanus Gmelin, 1789, through subsequent designation by Fowler 1908: 53. Diagnosis. See Compagno (1988) for a comprehensive diagnosis of Poroderma. Poroderma sharks are scyliorhinids with a stocky build; head slightly depressed; nasal barbels much longer than their basal diameter; mouths with labial furrows on both the upper and lower jaws; 1st dorsal fin larger than 2nd dorsal fin; origin of 1st dorsal fin posterior to the pelvic fin insertion; pelvic fins variably, but never completely, fused in males; claspers short and stubby, outer length three times that of their width at the base. Common name. Compagno (1988) and Compagno et al. (1989) referred to this genus as the barbeled catsharks. Remarks. Smith (1837) proposed the genus Poroderma, without describing it, as a replacement to the generic name Scyllium Cuvier, 1816, for the species Scyllium africanum (Gmelin, 1789) (wrongly attributed to Cuvier by Smith), Poroderma pantherinum (Smith in Müller and Henle, 1838) (given by name only in Smith 1837), P. submaculatum Smith, 1837 and P. variegatum Smith, 1837. Poroderma remained uncharacterised until Garman (1913) (Compagno 1984b, 1988). Although four species were named for this genus, the type species for Poroderma was subsequently designated by Fowler (1908) to be Squalus africanum, and placed Scyliorhinus stellaris (Linnaeus, 1758) in Poroderma in the same account. Fowler (1934) proposed Conoporoderma as a subgenus of Poroderma for P. pantherinum (the type species for the subgenus) and his new species P. marleyi Fowler, 1934. The subgenus was erected on the basis that the species he placed in this genus had long nasal barbels. Bigelow and Schroeder (1948) synonymised Poroderma with Scyliorhinus, and since P. africanum was the type for Poroderma, they raised Conoporoderma to the rank of genus for the remaining species P. marleyi and P. pantherinum; however, P. africanum was almost immediately returned to the genus Poroderma (Smith 1949). The synonymy of P. marleyi with P. pantherinum (see Remarks for P. pantherinum) dictates that the subgenus Conoporoderma would exist only for P. pantherinum. However, the relatively long nasal barbels of P. pantherinum compared to P. africanum amounts to species differentiation, as determined by this study, and this difference alone is insufficient to justify the existence of a subgenus for P. pantherinum. Therefore, the author agrees in synonymising Conoporoderma with Poroderma, following Bass et al. (1975), Springer (1979), and Compagno (1984b, 1988). Garman (1913), Fowler (1941), Bass et al. (1975), Springer (1979), and Compagno (1984b, 1988) have diagnosed this genus. Günther (1870), Garman (1913), Fowler (1941), Smith (1949), Bass et al. (1975), and Springer (1979) describe Poroderma as lacking labial furrows on the upper lip. Bass et al. (1975) and Springer (1979) explain that the folds on the upper lip are not true labial furrows. All Poroderma specimens examined in this study had small to large labial folds present on the upper lip, and skeletonisation by the author of many Poroderma specimens of both species has shown that a labial cartilage is associated with the upper labial furrow in all instances, which should therefore be considered a true labial furrow. Compagno (1984b) similarly diagnosed Poroderma as having true upper labial furrows. Most Scyliorhinus species, the genus to which Poroderma is most closely allied to (Springer 1979; Compagno 1984b, 1988), have a nasal barbel, however it is not as well developed as in Poroderma (Garman 1913; Springer 1979; Compagno 1984b, 1988); in addition, Poroderma has a true upper labial furrow, whereas Scyliorhinus does not (Compagno 1984b, 1988). Two species are recognised in this study, P. africanum and P. pantherinum. Both are abundant and endemic to South Africa. Etymology. The derivation of Poroderma was not given by Smith (1837). It is possible that the generic name is based on the Greek words poros, meaning hole or passage, and deros, meaning skin or hide. If this derivation is correct, it is unclear what Smith was referring to in these sharks, as they have rather tough hides with pores not enlarged. Distribution. The genus Poroderma Smith, 1837 is endemic to South Africa and contains two valid taxa as determined by this study, P. africanum (Gmelin, 1789), and P. pantherinum (Smith in Müller and Henle, 1838). Both Poroderma species are largely sympatric and are distributed along the South African coastline: P. africanum from Saldanha Bay on the west coast to north of East London on the east coast, and P. pantherinum from Cape Town on the west coast to Durban on the east coast (Bass et al. 1975; Compagno 1984b; current study). Bass et al. (1975) suggest that the central point of the distribution of P. pantherinum is Algoa Bay, and Bass (1986) states that this species is less abundant than P. africanum in shallow waters of the southwest Cape. The author encountered P. pantherinum and P. africanum with about equal frequency in Western Cape waters, and the apparent abundance of P. pantherinum in Eastern Cape waters may be a perceptual artefact due to the decreased abundance of P. africanum in the Eastern Cape, however it may occupy a niche in the absence of P. africanum and may explain why the larger specimens of P. pantherinum are found in the Eastern Cape. Tagging and anecdotal evidence suggest that Poroderma sharks have a limited home range and are philopatric. The author attempted a population genetic study on this genus (Human et al. 2001) to address the apparent philopatry of these sharks, and to determine whether the colour pattern variation observed in P. pantherinum was due to population differentiation. The attempt was unsuccessful and a future study into this aspect of Poroderma is needed. Key to the species of the genus Poroderma 1a. Nasal barbels less than one half the preoral length and not reaching the upper lip; prenarial length less than 0.9 times the mouth length, bold black stripes running parallel from snout tip to tail on the dorsal surface, background colouration pale to dark grey....................................................................................................................... P. africanum 1b. Nasal barbels greater than one half the preoral length and overhanging the upper lip; prenarial length more than 1.1 times the mouth length, combinations of black rosettes, small to large spots and stripes variably present or absent on the dorsal surface, background dorsal colouration pale grey to glossy jet black.......................... P. pantherinumPublished as part of Brett A. Human, 2006, A taxonomic revision of the catshark genus Poroderma Smith, 1837 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)., pp. 1-32 in Zootaxa 1229 on pages 3-
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Haploblepharus Garman
No full text[[Genus Haploblepharus Garman]] Introduction Many species of scyliorhinid sharks in South Africa are common to abundant, such as those from the genera Halaelurus, Haploblepharus, Holohalaelurus (in part), Poroderma, and Scyliorhinus. Southern Africa has an unusually high percentage of scyliorhinid endemics with a total of two endemic genera and thirteen endemic species (Compagno et al, 1989; Compagno & Human, 2003; Human, 2003, 2006a, 2006b; Human & Compagno, 2006). Another unique feature of southern African scyliorhinids is their inshore habit. Typically, most scyliorhinids are found on the continental shelf or continental slope in waters greater than one hundred meters in depth (Springer, 1979). In particular, species from the genera Haploblepharus and Poroderma are commonly seen close to shore in kelp forests and/or on rocky reefs by anglers and divers in South Africa (pers. obs.). Only limited catch data are available for Haploblepharus sharks because, when and if recorded, all species are lumped into the category “shyshark” or “unspecified shark” (Guastella, 1993; Pradervand, 1999). The low catches of “shyshark” reported by Guastella (1993) and Pradervand (1999) are due to a lack of reporting rather than low catch rates (pers. obs.). The greatest source of fishing pressure for Haploblepharus sharks probably comes from line fishing, both commercial and recreational, where persecution of these sharks exists (pers. obs.), with other sources of fishing pressure including commercial demersal trawls and, for H. edwardsii, H. pictus and to a lesser extent H. fuscus, the aquarium trade (pers. obs.). Another source of fishing pressure, on the west coast at least, are crayfish traps which apparently catch more Haploblepharus than demersal trawls, (D. Ebert, pers. comm.). Due to the heavy fishing of scyliorhinid species in southern African waters, either directed or as bycatch, and the apparent rarity of some forms, it is necessary to understand the scyliorhinid biodiversity of the region to properly manage and conserve these sharks. The morphological conservation within the group and varying colour patterns, particularly in H. pictus, has made species identification problematic within the genus. Species identification of this group has been historically problematic and stems from the use of colour patterns, that have proven to be variable, and poor choice of morphological characters in species identification keys. Juvenile specimens that are difficult to identify with confidence further complicate species identification, and it is possible that hybridisation may be occurring between species of this genus. Many of the registered specimens that were examined in the current study proved to be misidentified, and this study aims to provide a baseline for species identification, and highlight issues of species identification in this genus that require further research. It is hoped that increasing identification accuracy will encourage more accurate catch data reporting and research on these sharks, as there are still many unanswered questions, particularly for Haploblepharus of the Eastern Cape and kwaZulu-Natal.Published as part of Brett A. Human, 2007, A taxonomic revision of the catshark genus Haploblepharus Garman 1913 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)., pp. 1-40 in Zootaxa 1451 on page
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Haploblepharus Garman
No full text[[Genus Haploblepharus Garman]] The genus Haploblepharus Garman 1913 is a little known group of small to medium-sized catsharks (family Scyliorhinidae Gill 1862) endemic to southern Africa and ranging along the coasts of Namibia and South Africa. Three species of Haploblepharus are currently recognised (Human, 2003, in prep.), H. edwardsii (Schinz 1822), H. pictus (Müller & Henle 1838), and H. fuscus Smith 1950. Species identification of this group has been historically problematic and stems from the use of colour patterns and poor morphological characters in species identification keys. Under the name of H. edwardsii, Bass et al. (1975) illustrated a female Haploblepharus specimen taken from kwaZulu-Natal, South Africa, that they referred to as the “Natal” form, as opposed to the better known and more abundant “Cape” form from the south coast of South Africa. Bass et al. found the two forms to be morphologically identical, differing only in colour pattern, but suggested that they might represent separate species on the basis of different habitats and allopatric distribution. Springer (1979), in his review of the Scyliorhinidae, apparently considered the “Natal” form as a colour variant of H. edwardsii. Compagno (1984b, 1988) and Compagno et al. (1989) discussed the alternates of the two forms being regional colour variants or separate species without choosing an alternative, while Compagno (1999), Compagno & Human (2003), Compagno et al. (2005) and Human et al. (2006) considered the “Natal” form as an undescribed species. In the current study, and as part of a revision of the genus Haploblepharus (Human, 2003, in prep.), we show that the “Natal” form of Bass et al. (1975) differs significantly from H. edwardsii in morphological characters in addition to its colour pattern and warrants the rank of species.Published as part of Brett A. Human & Leonard J. V. Compagno, 2006, Description of Haploblepharus kistnasamyi, a new catshark (Chondrichthyes: Scyliorhinidae) from South Africa., pp. 41-58 in Zootaxa 1318 on page 4
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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