Shrew

Shrews are creatures of the kingdom Carpozoa descended from the Shrew Lizard. Shrews in general bear several similarities to mammals on Earth. They produce milk for their young just like mammals, and most species have a marsupium in which they raise their young. Most shrews, like the majority of Carpozoa, have six eyes, and all the shrews have at least a rudimentary sense of hearing inherited from the Shrew Lizard. The vast majority of extant species are warm-blooded, though they were ancestrally cold-blooded--endothermy evolved completely independently in furred shrews and bubbleskins. The only living cold-blooded shrews are the Soriparasites.

There are two major branches of Shrew, the furred shrews and the blood shrews. Furred shrews retain a fairly mammalian appearance, while blood shrews took on more varied appearances. Today, furred shrews are only represented by descendants of the Marine Tamow and the Beach Cheekhorn while blood shrews are only represented by the decidedly not-mammal-like Bubbleskins and Soriparasites.

Anatomy
Shrews typically have four limbs. Though they evolved from pentapeds, the tail remains flexible and tail-like, as it was in their direct ancestors. They typically have heterodont teeth, including pointed canine teeth. Most shrews have a pouch, generally located on the belly or between the legs, which is used to incubate their altricial young. They produce milk inside the pouch, which their offspring drink for nourishment. As spondylozoans, they typically have 6 eyes, and their nostrils are located on their faces, usually at or near the tip of the snout. Most modern shrews are warm-blooded with only a few cold-blooded species surviving to the present day, though naked cold-blooded shrews were commonplace prior to the ice age.

Like other caudopodosaurs, shrews ancestrally had a single, backwards-pointing knee on each leg. Furred shrews and blood shrews independently modified their hind scapulas into additional limb segments, however, thus most living shrews have 2 knees. The only living shrews which retain the single knee are the soriparasites.



Integument
The two major extant lineages of shrew have very different approaches to insulation.

Furred shrews, as their name suggests, have fur. This is similar to mammalian fur in that it is filamentous, made of keratin, and has a follicle. It provides insulation in a manner similar to fur, feathers, and setae on Earth.

Bubbleskins have a unique approach to insulation. Rather than fur, each of their keratinous scales has a hollow air-filled core. Though anatomically very different, they work on a similar principle--heat stays inside the body because it has difficulty being transferred through the air pockets in the bubbly scales.

Behavior
As there are many types of shrew, their behavior is extremely varied. All shrews have parental care.

Intelligence
Shrews have rarely developed high intelligence. Dromaeocanid shrews developed ape-like intelligence, but they were wiped out by the Shrew Plague and never produced a sapient species.

The Beach Cheekhorn is roughly as smart as a pig, while the Marine Tamow seems to be at least as smart as a beaver. As these are the ancestors of living furred shrews, they are currently predisposed to higher intelligence than Terran mammals, though some such as neoshrews break this trend.

The Tamjack and its descendants seem to show higher intelligence than their relatives, shown by their advanced boat-making capabilities. Most notably among them, shrogs developed high intelligence that can be likened to that of great apes, a first since the extinction of the dromaeocanids.

Breathing and Blood
Shrews have red, iron-based blood. Their have lungs and require air to breathe.

Diet & Energy
Shrews have varied diets, with many being herbivores or omnivores. Blood shrews, including bubbleskins, were ancestrally hemophagus, as their name suggests.

Evolutionary History
Shrews originated in Glicker, first evolving in Generation 64. The first appearance of fur in what would become the furred shrews was in Generation 67. Blood shrews first evolved in Generation 69, and the first Bubbleskin appeared in Generation 138.



Shrews experienced a significant radiation all over Glicker when they first evolved, spreading to nearly every biome on the continent and even to the nearby Yokto Island.

Most of the shrews, even the Shrew Lizard, were wiped out by a deadly plague in generation 95. This plague was spread by one of their parasitic members, the Death Soriparasite. All extant shrews at the time went extinct except for the Bearded Shrew, the River Shrew, the Soriparasite, and the Night Glider. This left distinct "east" and "west" populations, with the Shrews in eastern Glicker being naked blood shrews and those in western Glicker being warm-blooded furred shrews. The bearded shrew and most soriparasites would soon also go extinct due to the gamma-ray burst, which ultimately left only the Beach Shrotter, the Cave Night Glider, the Velishroot, and the Desert Soriparasite. Apart from the sole survivor of the soriparasites, which would remain isolated in Rabid Sandstone Caves for millions of years, these would go on to radiate into a diverse variety of forms.

As life recovered from the gamma-ray burst, pelagic marine Shrews descended from the Shrotter appeared and established themselves in LadyM Ocean, eventually crossing over into Wright. Around the same time, another Shrew, Xolagoba, also rafted across LadyM Ocean and established itself. A particular descendant of the Xolagoba, the Joviglut, went on to diversify all over wright. Meanwhile, Glicker saw the rise of new clades of megafaunal Shrews, such as Chuts and Froots. Blood Shrews also exited the caves, producing a myriad of hemophagic predators. However, when the ice comet impact event struct in Week 19, all megafaunal Shrews were wiped out. This also included nearly all furred shrews in Glicker, with the final population of Taigashroots and Marshroots soon going extinct from a severe drought which swept through their limited range. This left Glicker with only Blood Shrews and Wright with only Furred Shrews. When the continents began to break apart in week 20, only Drake was devoid of Shrews. Jaydoh was actually briefly home to its own endemic Shrews at this time, unrelated to the ones that would reclaim the island later.

When the ice age began, most blood shrews became extinct, as they were cold-blooded and ill-suited to the changing climate. However, in Dixon and Barlowe--what was previously known as Wright--the warm-blooded furred shrews had greater success, taking over the continent.

When the snowball event occured, all Shrews went extinct except for the Whiskerpick, the Bubbleskin, the Desert Soriparasite (which remained isolated in its cave), and their respective descendants. When the ice receded, while Bubbleskins continued to diversify and thrive across different parts of the world, especially Drake and Vivus, the surviving furred shrews were restricted mostly to Jaydoh. Two small populations of Iciclebacks actually survived in Barlowe, but they became extinct from habitat loss without producing descendants.

As an island continent, Jaydoh developed a unique assemblage of creatures, including megafaunal shrews. A clade of semi-aquatic Shrews comparable to Terran beavers originated there and spread outwards to Dixon, Barlowe, and surrounding islands. At around the same time, one of the megafaunal shrews shrank down and began to climb both cliffs and certain species of flora. This latter species, known as the Beach Cheekhorn, would develop a relationship with the Tlukvaequabora and subsequently spread to Barlowe and Dixon. As the sea levels rose, Jaydoh eventually sank. When this occurred, all furred shrews apart from descendants of the Marine Tamow and Beach Cheekhorn became extinct. At the same time, the rising sea levels also flooded Rabid Sandstone Caves, finally resulting in the extinction of the Desert Soriparasite though not before it gave rise to a descendant that finally left the caves behind known as the Lazarus Soriparasite.

This leaves a subgroup of Tams and the Beach Cheekhorn as the two living groups of furred shrews, with the two groups going down different paths. While the Beach Cheekhorn remained uncommon and fell into irrelevance in the ecosystems it survived in, the Tams have since diversified into many new forms, primarily in the aforementioned Dixon and Barlowe. However, some Shrews remained semi-aquatic, advancing their ability to construct their floating nests and eventually producing more otter-like forms. This eventually lead up to the Seashrog, which, thanks to the supercontinent leaving the ocean free of climate barriers, became the first single species of Shrew to be present on every single landmass. As a result, as of Week 26, at least one species of Shrew is present on even the most isolated islands. It has yet to be seen if the cosmopolitan status of this clade will last, however.

Locomotion
Among extant shrews, most furred shrews are quadrupeds while most bubbleskins are bipeds. In general, similar to Terran mammals, Shrew locomotion is hind limb-powered.

Among aquatic Shrews, if they propel themselves with their tail they typically use an up-down motion. There are two notable exceptions to this general rule, however, where they instead use a left-right undulation like a Terran fish instead. The first and earliest case of this method of swimming are the shrotters which lasted from the beginning of the Allenian to the end of the Somanian, which was when they became extinct due to an ice comet impact event. The second case of an aquatic shrew using side to side locomotion of the tail is the shrogger, a type of shrog that evolved in the late Bonoian.

Reproduction
Shrews ancestrally brooded fetal young inside a pouch and fed them milk, much like a Terran marsupial. A handful of branches, most notably the tamjacks, have developed a placenta. Bubbleskins lost the ability to produce milk secondarily, instead feeding their offspring regurgitated blood. All shrews perform parental care, which has never been lost in any species.

Ancestrally, shrews had internal testes and mated via cloacal kiss. This state is preserved in many basal species (excluding the cynovenator, which has hemipenes) and all blood shrews (including bubbleskins). Most living furred shrews, however, have similar external reproductive anatomy to Terran eutherian mammals, including external testes. A notable exception to the latter is the tamjacks, which re-evolved internal testes.

Senses
Shrews ancestrally possess the ability to hear. Furred shrews have pinnae. Several blood shrews evolved more advanced ears independently, but the extant bubbleskins and soriparasites lack any external ears and must hear using their jaw bones like the original Shrew Lizard did.

Shrews have nostrils on the end of their nose which allows them to smell. Like most Carpozoans, they have 6 eyes.

Size
Shrews come in many sizes. They are generally small, but megafaunal Shrews are possible and have appeared many times throughout Sagan IV's history.

Extant
Most living furred shrews are tams. Basal tams were armored, however many of their descendants lost that armor independently.

Neoshrews are among the most traditionally mammal-like living shrews.

Twintails are an odd subgroup of neoshrews which are genetically unstable and have duplicate spinal columns, granting them an extra tail.

Tamjacks are descendants of the tamjack which build structurally complex nests using logs, which they obtain by sawing down trees with their tails.

Shrogs are a tool-using subgroup of tamjacks which are among the smartest living shrews.

Cheekhorns are the only living non-tam furred shrews. They are large herbivores which, as their name implies, have horns on their cheeks.

Extinct
Shrotters were largely aquatic shrews which swam with a left-right undulation of their body and tail and often had distinctive barbels on their faces. Some species were tool-users. Shrotters died out as a result of the ice-comet impact event.

Dromaeocanid shrews were intelligent, bipedal species which were prominent predators over much of central and northern Glicker prior to their extinction. They were wiped out by the Shrew Plague.

Chuts were large herbivores with distinctly large heads. Most species were wiped out by a local meteor impact, and the last species died out when the cave it resided in was flooded following the ice comet impact event.

Succeeded
These are evolutionary grades in the ancestry of living furred shrews. They have living descendants, but all species of their general morphology are extinct.

Succeeded
These are evolutionary grades in the ancestry of living blood shrews. They have living descendants, but all species of their general morphology are extinct.

Other
Basal shrews that fit into neither the blood shrew nor the furred shrew category are entirely extinct.

Meta

 * Although Sagan 4 has many other earth clones, Shrews, along with Nodents, are often disliked more than others for unclear reasons.
 * Although Shrews never produced a sapient species, the most well-known of all of Sagan 4's non-canon rejected sapients, the "Chimpus", was a Shrew (specifically, a dromaeocanid).