[Ichthyology • 2018] Bythaelurus stewarti • A New Microendemic Species of the Deep-water Catshark Genus Bythaelurus (Carcharhiniformes, Pentanchidae) from the northwestern Indian Ocean, with Investigations of Its Feeding Ecology, Generic Review and Identification Key ---ScRaBBlE

Bythaelurus stewarti  

Weigmann, Kaschner & Thiel, 2018

DOI:  10.1371/journal.pone.0207887 

Abstract

A new deep-water catshark, Bythaelurus stewarti, is described based on 121 examined specimens caught on the Error Seamount (Mount Error Guyot) in the northwestern Indian Ocean. The new species differs from all congeners in the restricted distribution, a higher spiral valve turn count and in the morphology of the dermal denticles. It is distinguished from its morphologically and geographically closest congener, B. hispidus (Alcock), by the larger size (maximum size 44 vs. 39 cm TL, maturity size of males 35–39 vs. 21–28 cm TL), darker fresh coloration and dark grayish-brown mottling of the ventral head (vs. ventral head typically uniformly yellowish or whitish). Furthermore, it has a strongly different morphology of dermal denticles, in particular smaller and less elongate branchial, trunk and lateral caudal denticles that are set much less densely and have a surface that is very strongly and fully structured by reticulations (vs. structured by reticulations only in basal fourth). In addition, the new species differs from B. hispidus in having more slender claspers that are gradually narrowing to the bluntly pointed tip without knob-like apex (vs. claspers broader and with distinct knob-like apex), more spiral valve turns (11–12 vs. 8–10) and numerous statistical differences in morphometrics. A review of and a key to the species of Bythaelurus are given.

Fig 1. Bythaelurus stewarti n. sp., holotype, ZMH 26251, adult male, 425 mm TL, in (A) lateral, (B) dorsal, and (C) ventral views. Scale bar: 5 cm.

 Fig 2. Bythaelurus stewarti n. sp., (A) paratype, ZMH 26253, gravid female, 425 mm TL, (B) paratype, ZMH 26252, juvenile male, 340 mm TL, and (C) paratype, ZMH 26253, female embryo, 137.3 mm TL in lateral views. Scale bars: 5 cm.

Bythaelurus stewarti Weigmann, Kaschner & Thiel n. sp.

Error Seamount Catshark

Diagnosis: A medium-sized Bythaelurus species with the following characteristics: body firm and slender; snout long (preorbital length 4.9–7.4% TL) and broad, bell-shaped in dorsoventral view with distinct lateral indention; pre-outer nostril length 0.6–1.4 times internarial space; preorbital snout length 0.7–1.1 times interorbital space; preoral snout length 0.8–1.7 times in mouth width; eye length 10.2–15.5 times in predorsal distance, 4.9–7.7 times in head length and 1.2–2.3 times eye height; head length 2.2–2.6 times width at level of maximum outer extent of anterior nostrils; head width at level of maximum outer extent of anterior nostrils 1.1–1.3 times width at level of lateral indention of head, 1.2–1.6 times preorbital length, and 8.1–10.1% TL; tongue and roof of mouth densely set with knob-like oral papillae; pelvic-fin anterior margin 1.6–3.5 times in pectoral-fin anterior margin; first dorsal-fin base 1.3–2.3 times in interdorsal space; length of second dorsal-fin inner margin 0.8–2.3 times in second dorsal-fin height; second dorsal-fin base length 5.1–8.9% TL; anal-fin base 0.7–1.9 times interdorsal space. Coloration: dorsally dark grayish-brown with rather indistinct dark blotches at nape, on flank, below both dorsal fins, and across caudal fin; ventral side grayish-white, usually with dark grayish-brown mottling on head. Upper jaw with 64–85 and lower jaw with 64–88 rows of small tricuspidate teeth with outer surface of crown furrowed by strong longitudinal ridges and strongly structured by reticulations; monospondylous trunk vertebrae centra 37–42, diplospondylous precaudal centra 37–45, total centra 125–140. Branchial, trunk and lateral caudal-fin dermal denticles loosely set, their surface very strongly and fully structured by reticulations. Claspers rather long and very slender, gradually narrowing to bluntly pointed tip without knob-like apex, inner margin length 10.1–11.3% TL, base width 1.4–1.5% TL; clasper hooks present along inner edge of large exorhipidion, large envelope overlapping part of clasper groove, inner lobe with rhipidion, cover rhipidion, pseudopera and pseudosiphon. The reproductive mode is yolk-sac viviparous. Bythaelurus stewarti n. sp. differs from all congeners in the distribution, which is apparently restricted to the Error Seamount. It further differs from all congeners in a higher spiral valve turn count (11–12 vs. 6–10) and in the morphology of branchial, trunk and lateral caudal-fin dermal denticles, which are loosely-spaced and not overlapping even in adult specimens of the new species, whereas they are closely-set and overlapping in all other Bythaelurus species. Compared to its morphologically and geographically closest congener, the new species further differs in a larger size, a ventral head with dark mottling, claspers that gradually narrow to the bluntly pointed tip without knob-like apex, and a surface of dermal denticles that is very strongly and fully structured by reticulations.

Fig 18. Map of the Indian Ocean depicting the verified occurrences of nine species of Bythaelurus in the Indian Ocean.
The occurrences are based on examined material except for B. clevai (based on one examined specimen plus catch locations of the type specimens taken from Séret [12] and B. alcockii (no specimen available, catch location of the lost holotype indicated as Arabian Sea in Garman [40]). Bythaelurus alcockii: black pentagon, B. bachi: black stars, B. clevai: white triangles, B. hispidus: black (holotype) and white (other specimens) circles, B. lutarius: black triangles, B. naylori: white stars, B. stewarti n. sp.: black and white diamonds, B. tenuicephalus: white squares, B. vivaldii: black square. Inset of the Gulf of Aden area depicts the catch locations of the holotype (black diamond) and paratypes (black and white diamonds) of Bythaelurus stewarti n. sp. on Error Seamount and catch locations of 100 comparative specimens of B. hispidus from off the Socotra Islands (white circles). Country abbreviations follow ISO 3166–1 (OM = Oman, SO = Somalia, YE = Yemen).

Distribution: The new species is known only from the Error Seamount (Mount Error Guyot) in 380–420 m depth (see map in the Discussion section). It is apparently a microendemic species restricted to this isolated Seamount.

Etymology: The new species is named after the late filmmaker and shark conservationist Rob Stewart, who inspired the second author and stimulated her interest in sharks.

Simon Weigmann, Carina Julia Kaschner and Ralf Thiel. 2018. A New Microendemic Species of the Deep-water Catshark Genus Bythaelurus (Carcharhiniformes, Pentanchidae) from the northwestern Indian Ocean, with Investigations of Its Feeding Ecology, Generic Review and Identification Key.  PLoS ONE. 13(12): e0207887. DOI:  10.1371/journal.pone.0207887

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روابط التحميل والمشاهدة، الروابط المباشرة للتحميل

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شاهد هذا الفيديو القصير لطريقة التحميل البسيطة

منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات

كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا

شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا

رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا
شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا

تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا

ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.

[Ichthyology • 2019] Carcharhinus obsolerus • Lost before Found: A New Species of Whaler Shark (Carcharhiniformes: Carcharhinidae) from the Western Central Pacific known only from Historic Records ---ScRaBBlE

Carcharhinus obsolerus

White, Kyne & Harris, 2019

Lost Shark  || DOI: 10.1371/journal.pone.0209387  

Painting by Lindsay Marshall (www.stickfigurefish.com.au) 

twitter.com/WillWhitesharks

Abstract

Carcharhinus obsolerus is described based on three specimens from Borneo, Thailand and Vietnam in the Western Central Pacific. It belongs to the porosus subgroup which is characterised by having the second dorsal-fin insertion opposite the anal-fin midbase. It most closely resembles C. borneensis but differs in tooth morphology and counts and a number of morphological characters, including lack of enlarged hyomandibular pores which are diagnostic of C. borneensis. The historic range of C. obsolerus sp. nov. is under intense fishing pressure and this species has not been recorded anywhere in over 80 years. There is an urgent need to assess its extinction risk status for the IUCN Red List of Threatened Species. With so few known records, there is a possibility that Carcharhinus obsolerus sp. nov. has been lost from the marine environment before any understanding could be gained of its full historic distribution, biology, ecosystem role, and importance in local fisheries.

Fig 1. Lateral view of Carcharhinus obsolerus sp. nov. (NMW 61463; female holotype 433 mm TL).
A. Preserved specimen; B. Painting by Lindsay Marshall (www.stickfigurefish.com.au). 

Fig 2. Head of Carcharhinus obsolerus sp. nov. (NMW 61463; Holotype). 433 mm TL female:
A. lateral view; B. ventral view.

Fig 5. In situ teeth of Carcharhinus obsolerus sp. nov. (ANSP 77121, paratype). 370 mm TL female:
A. upper teeth; B. lower teeth.

Carcharhinus obsolerus White, Kyne & Harris sp. nov.  

Synonymy: Carcharhinus sp.: [Compagno, 1979]: 517, 520, 523, 536 (Borneo); [Compagno, 1988]: 319, 321, 327 (Vietnam, Borneo, and Thailand); [Compagno et al., 1998]: 1359, fig (Vietnam, Borneo, and Thailand)

Carcharhinus porosus: [Compagno et al., 2005]: 71 (Borneo, Saigon, and Bangkok)

Carcharhinus undescribed small species: [Compagno, 1984]: 497 (Borneo, Vietnam, and Thailand)

Carcharhinus sp. (= ‘Carcharhinus porosus’): [Compagno et al., 1998]: 1322.

Carcharhinus sp. A: [Compagno et al., 2005]: 307, fig, pl. 62 (Borneo, Vietnam, and Thailand); [Voigt et al., 2011]: 103, fig 50

Holotype: NMW 61463, female 433 mm TL, Bangkok, Thailand, no date or collector recorded.

Paratypes: ANSP 76859, female late-term embryo 339 mm TL, Ho Chi Minh City, Vietnam, Dec. 1934, coll. H. Rutherfurd; ANSP 77121 (paratype of Carcharhinus tephrodes Fowler), female 370 mm TL, Baram, Sarawak, Malaysian Borneo, 1897, coll. A.C. Harrison Jr. & H.M. Hiller.

Diagnosis.: A small species of Carcharhinus with: a slender body and tail; no interdorsal ridge; head parabolic in dorsal view, relatively wide, interorbital space 11.2–12.0% TL; eyes relatively large, length 2.4–2.9% TL, 10.0–15.1 times in head length; no row of enlarged hyomandibular pores alongside each mouth corner; upper anterior teeth broadly triangular and serrated, with large and coarse (non-lobate) serrations basally; lower anterior teeth with narrower, mostly straight cusps; cusps of upper and lower anterolateral teeth with apical margin slightly recurved; no lateral cusplets; total tooth row counts 27–31/26–29; posterior edge of the mandibular plate with an elongate and crescentic indentation; second dorsal-fin origin well posterior of anal-fin origin, about opposite anal-fin midbase, second dorsal-fin origin to anal-fin origin 1.3–2.5% TL, 0.3–0.6 times second dorsal-fin base; first dorsal fin triangular, not falcate, origin about opposite first third of pectoral-fin inner margin length, free rear tip just anterior to pelvic-fin origins, length 1.7–1.9 times height, inner margin 1.9–2.5 in base; second dorsal fin much smaller than first, slightly smaller than anal fin; base 1.4–2.0 times height; height 22–31% of first dorsal-fin height; anal fin height 1.2–1.5 times second dorsal height, base 1.1–1.2 times second dorsal-fin base; total vertebral counts 114–120, monospondylous precaudal counts 36–40, diplospondylous precaudal counts 18–19, diplospondylous caudal counts 56–66, precaudal counts 54–58; no distinct black markings on fins.

....

Distribution: Uncertain; collection records indicate southern South China Sea (Gulf of Thailand, Vietnam, Malaysian Borneo).

The distribution of Carcharhinus obsolerus is uncertain. Given that this species has not been seen in many decades, a better understanding of the distribution of this species is unlikely unless archaeological or paleontological records are found. While Baram in Sarawak is likely an accurate collection locality, both Bangkok and Ho Chi Minh City specimens may have been caught in other South-east Asian locations and brought into these cities where bigger markets exist. Thus, there is a possibility it had a much more restricted distribution than the three known specimens allude to, but it cannot be ruled out that it had a wider distribution in the South-east Asian region.

Etymology: The specific name is Latin for ‘extinct’ (obsolerus) in allusion to the fact that the species has not been recorded in many decades. Proposed English vernacular name: Lost Shark.

William T. White, Peter M. Kyne and Mark Harris. 2019. Lost before Found: A New Species of Whaler Shark Carcharhinus obsolerus from the Western Central Pacific known only from Historic Records. PLoS ONE. 14(1): e0209387. DOI: 10.1371/journal.pone.0209387  

twitter.com/WillWhitesharks/status/1080544017845112832

        

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روابط التحميل والمشاهدة، الروابط المباشرة للتحميل

من هنا

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شاهد هذا الفيديو القصير لطريقة التحميل البسيطة

منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات

كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا

شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا

رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا
شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا

تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا

ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.

[PaleoIchthyology • 2018] Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction ---ScRaBBlE

in Bazzi, Kear, Blom,et al., 2018.

 DOI: 10.1016/j.cub.2018.05.093 

Highlights: 

• Shark teeth reveal morphological turnover during the end-Cretaceous mass extinction

• Fossil shark dental disparity is decoupled from taxonomic richness

 • Cretaceous–Palaeogene shark disparity was nearly static unlike other marine predators

• Prey availability and trophic cascades may have initiated Cenozoic shark radiations

Summary

The Cretaceous–Palaeogene (K–Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K–Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carcharhiniformes (Ground sharks). These clades are prevalent predators in today’s oceans, and were geographically widespread during the late Cretaceous–early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K–Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing low-crowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K–Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod and pelagic amniote groups, as well as the explosive radiation of middle trophic-level teleost fishes. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic.

Keywords: K–Pg Boundary, Geometric Morphometrics, Sharks, Lamniformes, Carcharhiniformes, Macroevolution, Mass extinction, Teeth, Disparity

Late Maastrichtian marine assemblage.

 Illustration: Julius Csotonyi 

 Mohamad Bazzi, Benjamin P. Kear, Henning Blom, Per E. Ahlberg and Nicolás E.Campione. 2018. Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction. Current Biology. In Press.  DOI: 10.1016/j.cub.2018.05.093

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روابط التحميل والمشاهدة، الروابط المباشرة للتحميل

من هنا

او

من هنا

شاهد هذا الفيديو القصير لطريقة التحميل البسيطة

منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات

كيف تحصل على مدونة جاهزة بآلاف المواضيع والمشاركات من هنا

شاهد قناة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على اليوتيوب لمزيد من الشرح من هنا

رابط مدونة منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات في أي وقت حــــتى لو تم حذفها من هنا
شاهد صفحة منتدى مدونات بلوجر جاهزة بألاف المواضيع والمشاركات على الفيس بوك لمزيد من الشرح من هنا

تعرف على ترتيب مواضيع منتدى مدونات بلوجر جاهزة بآلاف المواضيع والمشاركات (حتى لا تختلط عليك الامور) من هنا

ملاحظة هامة: كل عمليات تنزيل، رفع، وتعديل المواضيع الجاهزة تتم بطريقة آلية، ونعتذر عن اي موضوع مخالف او مخل بالحياء مرفوع بالمدونات الجاهزة بآلاف المواضيع والمشاركات، ولكم ان تقوموا بحذف هذه المواضيع والمشاركات والطريقة بسيطة وسهلة. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــسلامـ.