New Shark Species Described to Science: American Pocket Shark (Mollisquama mississippiensis)

A new paper published in the journal Zootaxa describes a new kitefin shark species for the first time. Newly described Mollisquama mississippiensis sp. nov. belongs to the family Dalatiidae. This family contains 11 described species in seven genera. Dalatiidae sharks are found almost worldwide, preferring deepwater, open ocean habitats in temperate and tropical seas (Ebert, Fowler, & Dando, 2015). These sharks are distinct from other squaliform sharks by their robust lower jaw, heterodonty (Or habing multi tooth morphology), lack of an anal fin, and their dorsal fins that so not feature spines (Bigelow & Schroeder, 1948). Little is known about the biology and life history characteristics of these sharks, however, it is documented that they are viviparous, with their embryos developing inside the mom while attached to a yolk sac (Gadig & Gomes, 2002).

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Family Dalatiidae (1) Taillight Shark (Euprotomicrodes zantedeschia) (2) Pygmy Shark (Euprotomicrus bispinatus) (3) Kitefin Shark (Dalatias Iicha) (4) Longnose Pygmy Shark (Heteroscymnoides marleyi) (5) Cookiecutter Shark (Isistius brasiliensis) (6) South China Cookiecutter Shark (Isistius labialis(7) Largetooth Cookiecutter Shark (Isistius plutodus) (8) Pocket Shark (Mollisquama parini(9) Smalleye Pygmy Shark (Squaliolus aliae) (10) Spined Pygmy Shark (Squaliolus laticaudus) (Ebert, Fowler, & Dando, 2015)

 

The newest member of family Dalatiidae is the American Pocket Shark (Mollisquama mississippiensis sp. nov.) (Grace et al., 2019). This species was first discovered in February of 2010 while on a mid-water trawling research project to assess predator-prey dynamics of sperm whales (Physeter macrocephalus) in the Gulf of Mexico. The trawls ranged in depth from 15 feet (5 m) to a maximum depth of 1900 feet (580 m).

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Figure 7. Mollisquama mississippiensis sp. nov. capture site (*) (Grace et al., 2019).

 

The American pocket shark is a small shark species, reaching lengths of  only  5.5 inches (14.2 cm) and weighing only 0.03 lbs (14.6 g) (Grace et al., 2019). Their cylindrical body tappers into a slender caudual penduncle followed by a homocercal caudal fin. Their five pairs of gills are surrounded by a light cream patch over a dark coal gray body. Their two low dorsal fins are located just about the pelvic fin. This species is closely related to and resembles its cousin and only other member of genus Mollisquama, the Pocket Shark (Mollisquama parini). However, the American Pocket Shark differs from its cousin by having a pit organ centrally placed behind the lower jaw, photophores irregularly distributed along its body, a series of 16 photophore aggregations located ventral-abdominally, their upper teeth lack a labial-surface ridge, and their lower teeth have a week or absent basal sulcus. When this species was first captured in 2010, it was clearly discernible as a new species from their pit organ and photophore aggregations (Grace, Doosey, Bart, & Naylor, 2015).

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Figure 1. Mollisquama mississippiensis sp. nov., Illustrated to scale in (A) lateral and (B) ventral view (Grace et al., 2019).

 

Their jaws exhibit heterodonty (Grace et al., 2019).  Their upper teeth are narrow and cone-shaped without a surface ridge. While their lower teeth are broad and blade-like. In both the upper and lower jaw, the teeth gradually decrease in size as they move towards the corners of the mouth.

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Figure 2. Mollisquama mississippiensis sp. nov., upper tooth lateral view (tooth #4 right); lower tooth labial-surface view (Grace et al., 2019).

 

Possibly the most interesting talent of this shark is its ability to emit bursts of bioluminescent fluid. The American pocket shark, like the pocket shark, has a pair of pocket-like glands just behind their pectoral fins. It’s from this gland that the pocket sharks are likely able to project this bioluminescent fluid to distract potential predators.

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Grace, M. (Artist). (2019). Mollisquama mississippiensis artist rendition [Digital Image]. Retrieved from https://shark-references.com

I love seeing new species described for the first time! Over 70% of our planet is covered by our oceans, and yet we have only explored 5% of them (US Department of Commerce, National Oceanic and Atmospheric Administration, 2009)! It’s no surprise that new species are being discovered every year. –But don’t be holding your breath for any megalodons! They are well and truly extinct, sorry!

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Copley, J. (Author). (2014 October). It’s easy to ignore what we cannot see [Digital Image]. Retrieved from http://moocs.southampton.ac.uk/

Shark Stats

Authority: Grace, Doosey, Denton, Naylor, Bart & Maisey, 2019

Family: Dalatiidae, 11 species

Length: 5.5 inches (14.2 cm)

Weight: 0.03 lbs (14.6 g)

Habitat: Deepwater to midwater species, likely benthic

Depth: Caught between 15 feet (5 m) to a maximum depth of 1900 feet (580 m).

Reproduction: Ovoviviparity

Gestation: Unknown

Litter Range: Unknown

Home Range: Gulf of Mexico

Diet: Unknown

IUCN Status: Yet to be Assessed

(Grace, Doosey, Denton, Naylor, Bart & Maisey, 2019)

The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Proceeds benefit shark research and conservation with a donation to Project AWARE!

Thanks so much for checking out the Sixgill Sawshark! If you missed last week’s featured species, please be sure to check out the amazing Bigeye Thresher! If there is a species of elasmobranch you’d love to know more about, leave me a comment or send me a message! I would love to do a feature on your favorite species. Also connect with me on Instagram and Facebook for even more elasmo fun!

Conservation legislation needs public support in order to become law and help protect the environment and wildlife. Tell your representatives that you care about environmental and wildlife conservation. It only takes a moment to make a change that will last a lifetime. Until next time finactics!

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Featured Image Source

Grace et al (Authors). (2019). Millisquama mississippiensis sp. nov., Illustrated to scale in lateral view [Digital Image]. Retrieved from https://www.mapress.com/j/zt/article/view/zootaxa.4619.1.4/26619

Literature Cited

Bigelow, H.B. & Schroeder, W.C. (1948) Fishes of the Western North Atlantic. Part 1. Lancelets, Cyclostomes, Sharks. Memoirs
of the Sears Foundation for Marine Research, 1 (1), 59–576.

Ebert, D. A., Fowler, S. L., & Dando, M. (2015). Sharks of the world: a fully illustrated guide. Wild Nature Press.

Gadig, O. B. F., & Gomes, U. L. (2002). First report on embryos of Isistius brasiliensis. Journal of fish biology60(5), 1322-1325.

Grace, M. A., Doosey, M. H., Bart, H. L., & Naylor, G. J. (2015). First record of Mollisquama sp.(Chondrichthyes: Squaliformes: Dalatiidae) from the Gulf of Mexico, with a morphological comparison to the holotype description of Mollisquama parini Dolganov. Zootaxa3948(3), 587-600.

Grace, M. A., Doosey, M. H., Denton, J. S. S., Naylor, G. J. P., Bart, H. L. J., & Maisey, J. G. (2019). A new Western North Atlantic Ocean kitefin shark (Squaliformes: Dalatiidae) from the Gulf of Mexico. Zootaxa, 4619(1), 109–120.

US Department of Commerce, National Oceanic and Atmospheric Administration. (2009, January 01). How much of the ocean have we explored? Retrieved September 17, 2017, from https://oceanservice.noaa.gov/facts/exploration.html

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