Thor's hero shrew

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Thor's hero shrew
Temporal range: Recent
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Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Eulipotyphla
Family: Soricidae
Genus: Scutisorex
Species:
S. thori
Binomial name
Scutisorex thori
Stanley, Malekani & Gambalemoke in Stanley et al., 2013

Thor's hero shrew (Scutisorex thori) is an extant species of shrew native to the Democratic Republic of the Congo. It and its sister species, the hero shrew (Scutisorex somereni), are the only mammal species known to have interlocking vertebrae. [1]

Shrew family of mammals

The shrew is a small mole-like mammal classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, or the West Indies shrews, which belong to different families or orders.

Democratic Republic of the Congo Country in Central Africa

The Democratic Republic of the Congo, also known as DR Congo, the DRC, DROC, Congo-Kinshasa, or simply the Congo, is a country located in Central Africa. It is sometimes anachronistically referred to by its former name of Zaire, which was its official name between 1971 and 1997. It is, by area, the largest country in Sub-Saharan Africa, the second-largest in all of Africa, and the 11th-largest in the world. With a population of over 78 million, the Democratic Republic of the Congo is the most populated officially Francophone country, the fourth-most-populated country in Africa, and the 16th-most-populated country in the world.

A sister group or sister taxon is a phylogenetic term denoting the closest relatives of another given unit in an evolutionary tree. The expression is most easily illustrated by a cladogram:

Contents

Description

Thor's hero shrew has a smaller skull and fewer lower vertebrae—eight instead of ten or eleven—than its sister species. [2] [3] The vertebrae have fewer bony offshoots, and the animal's ribs are flatter and more robust. [2] [3] Like the hero shrew, it has an extremely strong back—roughly four times stronger than a human's, adjusted for size. [2] It is less than 1 foot (0.30 m) long and weighs approximately 1.7 ounces (48 g). Hero shrews are generally less flexible than most mammals, [4] but are able to turn around in confined spaces by sagittally flexing their spines. [5]

Sagittal plane

A sagittal plane, or longitudinal plane, is an anatomical plane which divides the body into right and left parts. The plane may be in the center of the body and split it into two halves (mid-sagittal) or away from the midline and split it into unequal parts (para-sagittal).

Discovery

Thor's hero shrew was first described in Biology Letters by a team headed by vertebrate biologist William Stanley. In July 2013. It was discovered when Stanley dissected a specimen of hero shrew collected in the village of Baleko and found that its spine was different from those of known specimens. [3] [4] The team named the shrew after Thorvald "Thor" Holmes, Jr of the Humboldt State University Vertebrate Museum, as well as referring to the Norse god Thor due to the god's association with strength. [5]

<i>Biology Letters</i> journal

Biology Letters is a peer-reviewed, biological, scientific journal published by the Royal Society. It focuses on the rapid publication of short high quality research articles, reviews and opinion pieces across the biological sciences. Biology Letters has an average turnaround time of twenty four days from submission to a first decision.

William T. "Bill" Stanley was an American mammalogist who was a manager of the collections at one of the world's largest natural history museums and a student of the mammals of eastern Africa. He was an evolutionary biologist and mammalogist, and at the time of his death was the Director of the Field Museum of Natural History's Collections Center and the Collection Manager of the Field Musem's Collection of Mammals. Stanley studied the biogeography, ecology, evolution, and systematics of shrews, bats and rodents that live on mountains within Tanzania and surrounding countries.

Humboldt State University university

Humboldt State University (HSU) or Humboldt State, also occasionally referred to as Humboldt, is a public university in Arcata, California. It is the northernmost campus of the 23-school California State University (CSU) system. The main campus, situated hillside at the edge of a coast redwood forest, has commanding views overlooking Arcata, much of Humboldt Bay, and the Pacific Ocean. The college town setting on the California North Coast, 8 miles (13 km) north of Eureka, 279 miles (449 km) north of San Francisco, and 654 miles (1052.51 km) north of Los Angeles is notable for its natural beauty.

Evolutionary significance

The structure of Thor's hero shrew's cranium and vertebrae suggest that it may be descended from an evolutionary intermediate between the hero shrew and other shrews. Its existence may help explain the evolution of the hero shrew which, Stanley explains, has historically been cited as an excellent example of punctuated equilibrium, a theory that holds that species sometimes evolve very rapidly in short periods of time after long periods of stability. The existence of an intermediate species hints at a more gradual or incremental evolution for the hero shrew's extreme specialization. [1]

Punctuated equilibrium theory in evolutionary biology

Punctuated equilibrium is a theory in evolutionary biology which proposes that once species appear in the fossil record the population will become stable, showing little evolutionary change for most of its geological history. This state of little or no morphological change is called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis. Cladogenesis is the process by which a species splits into two distinct species, rather than one species gradually transforming into another.

Thor's hero shrew may also help explain the evolutionary advantage of interlocking vertebrae. The animal's discoverers hypothesize that both hero shrew species use their strong backs to push under logs or rocks to find worms or to crawl into the tight spaces between the trunk and the bases of palm leaves to find larvae. [1] The proposed behavior has not been observed in the wild, [3] but the shrews are commonly seen in palm forests, where they have runways around the tree trunks. [5]

Related Research Articles

Vertebrate subphylum of chordates

Vertebrates comprise all species of animals within the subphylum Vertebrata. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,276 species described. Vertebrates include the jawless fishes and jawed vertebrates, which include the cartilaginous fishes and the bony fishes.

<i>Ichthyostega</i> genus of tetrapodomorphs (fossil)

Ichthyostega is an early genus of tetrapodomorphs that lived at the end of the Late Devonian Period. It was one of the first four-limbed vertebrates in the fossil record. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps. Although Ichthyostega is often labelled a "tetrapod" due to the possession of limbs and fingers, it was more basal ("primitive") than true crown-tetrapods, and could more accurately be referred to as a stegocephalian or stem tetrapod. Likewise, while undoubtedly of amphibian build and habit, it is not considered a true member of the group in the narrow sense, as the first modern amphibians appeared in the Triassic Period. Until finds of other early stegocephalians and closely related fishes in the late 20th century, Ichthyostega stood alone as a transitional fossil between fish and tetrapods, combining fish- and tetrapod-like features. Newer research has shown that it had an unusual anatomy, functioning more akin to a seal than a salamander, as previously assumed.

Solenodon genus of mammals

Solenodons are venomous, nocturnal, burrowing, insectivorous mammals belonging to the family Solenodontidae. The two living solenodon species are the Cuban solenodon, and the Hispaniolan solenodon.

Fish anatomy study of the form or morphology of fishes

Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.

<i>Dimetrodon</i> genus of synapsids

Dimetrodon is an extinct genus of synapsids that lived during the Cisuralian, around 295–272 million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the southwestern United States, the majority coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was first described in 1878.

<i>Deinocheirus</i> genus of reptiles (fossil)

Deinocheirus is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. In 1970, this specimen became the holotype of the only species within the genus, Deinocheirus mirificus; the genus name is Greek for "horrible hand". No further remains were discovered for almost fifty years, and its nature remained a mystery. Two more complete specimens were described in 2014, which shed light on many aspects of the animal. Parts of these new specimens had been looted from Mongolia some years before, but were repatriated in 2014.

<i>Lystrosaurus</i> Genus of Late Permian and Early Triassic dicynodont therapsids

Lystrosaurus was a herbivorous genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. They ranged in size from a small dog to 2.5 meters long.

Lesser white-toothed shrew species of mammal

The lesser white-toothed shrew is a tiny shrew with a widespread distribution in Africa, Asia and Europe. Its preferred habitat is scrub and gardens and it feeds on insects, worms, slugs, snails, newts and small rodents. The closely related Asian lesser white-toothed shrew was once included in this species, but is now considered to be a separate species.

Venomous mammal animal of the class Mammalia that produces venom, which it use to kill or disable prey, or to defend from predators or conspecifics

Venomous mammals are animals of the class Mammalia that produce venom, which they use to kill or disable prey, to defend themselves from predators or conspecifics or in agonistic encounters. In modern nature, venomous mammals are rare. Mammalian venoms form a heterogeneous group having different compositions and modes of action and are present in three orders of mammals, Eulipotyphla, Monotremata, and Chiroptera. A fourth order, Primates, is proposed to have venomous representatives. To explain the rarity of venom delivery in Mammalia, Mark Dufton of the University of Strathclyde has suggested that modern mammalian predators do not need venom because they are able to kill quickly with their teeth or claws, whereas venom, no matter how sophisticated, requires time to disable prey.

<i>Cetiosauriscus</i> genus of reptiles (fossil)

Cetiosauriscus is a genus of sauropod dinosaur that lived between 166 and 164 million years ago during the Callovian in what is now England. A herbivore, Cetiosauriscus had—for sauropod standards—a moderately long tail, and longer forelimbs, making them as long as its hindlimbs. It has been estimated as about 15 m (49 ft) long and between 4 and 10 t in weight.

<i>Ornithopsis</i> genus of reptiles (fossil)

Ornithopsis was a medium-sized Early Cretaceous sauropod dinosaur, from England.

Hero shrew species of shrew

The hero shrew, also known as the armored shrew, is a large shrew native to the Congo Basin of Africa. Its features are typical of a white-toothed shrew − short legs, slender snout, dense fur − except for a highly unusual spinal column. It has corrugated interlocking vertebrae that are unique among mammals except for its sister species, Thor's hero shrew. This unique adaptation allows the animal to bear a huge amount of weight on its back − 72 kg (159 lb) according to an expedition team.

<i>Scutisorex</i> genus of mammals of the subfamily Crocidurinae

Scutisorex is a genus of African shrews, mammals of the family Soricidae. Members of the genus are the only known mammal species whose vertebrae interlock, a feature which, along with the general enlargement and strengthening of the backbone and ribs, allows them to bear remarkable loads. They also have well developed muscles for flexing their spine in the sagittal plane. It is thought that these adaptations allow the shrews to wedge open spaces between the trunks of palm trees and the stems of dead leaves, as well underneath logs and rocks, allowing them to partake of a reliable source of insect larvae and earthworms that would otherwise be inaccessible.

<i>Amphicoelias</i> genus of reptiles (fossil)

Amphicoelias is a genus of herbivorous sauropod dinosaur that lived approximately 150 million years ago during the Tithonian of what is now Colorado, United States. A herbivore, Amphicoelias was moderately sized at about 25 m (82 ft) long–roughly the same length as Diplodocus, to which it was related. Its hindlimbs were very long and thin, and its forelimbs were proportionally longer than in relatives.

<i>Brachiosaurus</i> genus of reptiles (fossil)

Brachiosaurus is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154–153 million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in the Colorado River valley in western Colorado, United States. Riggs named the dinosaur Brachiosaurus altithorax; the generic name is Greek for "arm lizard", in reference to its proportionately long arms, and the specific name means "deep chest". Brachiosaurus is estimated to have been between 18 and 21 meters long; weight estimates range from 28.3 to 58 metric tons. It had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. Atypically, Brachiosaurus had longer forelimbs than hindlimbs, which resulted in a steeply inclined trunk, and a proportionally shorter tail.

<i>Aerosaurus</i> genus of synapsid

Aerosaurus is an extinct genus within Varanopidae, a family of non-mammalian synapsids. It lived between 252-299 million years ago during the Early Permian in North America. The name comes from Latin aes (aeris) “copper” and Greek sauros “lizard,” for El Cobre Canyon in northern New Mexico, where the type fossil was found and the site of former copper mines. Aerosaurus was a small to medium-bodied carnivorous synapsid characterized by its recurved teeth, triangular lateral temporal fenestra, and extended teeth row. Two species are recognized: A. greenleeorum (1937) and A. wellesi (1981).

<i>Pakasuchus</i> genus of crocodylomorphs

Pakasuchus is a genus of notosuchian crocodyliform distinguished by its unusual mammal-like appearance, including mammal-like teeth that would have given the animal the ability to chew. It also had long, slender legs and a doglike nose. Pakasuchus lived approximately 105 million years ago, in the mid-Cretaceous. Fossils have been found in the Galula Formation of Rukwa Rift Basin of southwestern Tanzania, and were described in 2010 in the journal Nature. The type species is P. kapilimai. Pakasuchus means "cat crocodile" in reference to its cat-like appearance and probable behavior.

Vertebra bone in the spinal column

In the vertebrate spinal column, each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate.

Spinolestes is an extinct mammal genus from the Early Cretaceous of Spain. A gobiconodontid eutriconodont, it is notable for the remarkable degree of preservation, offering profound insights to the biology of non-therian mammals.

References

  1. 1 2 3 Richard Johnston (July 24, 2013). "Shrew has a spine of godly strength". Nature. Retrieved July 24, 2013.
  2. 1 2 3 Melissa Hogenboom (July 24, 2013). "New species of super-strong 'Hero Shrew' discovered". BBC. Retrieved July 24, 2013.
  3. 1 2 3 4 Christine Dell'Amore (July 24, 2013). "Hero Shrew Found, One of 'Most Bizarre Animals on Earth'". National Geographic News. Retrieved July 25, 2013.
  4. 1 2 Jennifer Viegas (July 23, 2013). "This super 'hero' shrew has an unbreakable back". Discovery News. NBC. Retrieved July 25, 2013.
  5. 1 2 3 Stanley, W. T.; Robbins, L. W.; Malekani, J. M.; Mbalitini, S. G.; Migurimu, D. A.; Mukinzi, J. C.; Hulselmans, J.; Prevot, V.; Verheyen, E.; Hutterer, R.; Doty, J. B.; Monroe, B. P.; Nakazawa, Y. J.; Braden, Z.; Carroll, D.; Kerbis Peterhans, J. C.; Bates, J. M.; Esselstyn, J. A. (23 October 2013). "A new hero emerges: Another exceptional mammalian spine and its potential adaptive significance". Biology Letters . 9 (5): 20130486. doi:10.1098/rsbl.2013.0486. PMC   3971687 . PMID   23883579.