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 predominantly represented by whiskered shrews (more specifically 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.

Basal shrews, including soriparasites, have scaly skin.

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.

History
The ancestors of shrews were the prosubigosaurs, the pentapedal line of terrestrial spondylozoa which also gave rise to the dwellers and the capiris.

True 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.

Early Shrews
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. Some noteworthy families that existed around this time included the basal reptile-like shrew lizards, night gliders, and soriparasites, and the more derived fur-covered woolly shrews, wolf shrews, and kangashrews.

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.

Post-Gamma Ray Burst
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, the polydactyl Xolagoba, also rafted across LadyM Ocean and established itself. In Glicker, 'shroot'-grade shrews radiated into the large and rotund herbivorous chuts, the long-snouted carnivorous froots, and the beardshroots, a peculiar group which used blood-soaked chin fur as a mating display. In Wright, 'xolagoba'-grade shrews ruled the trees, taking on forms resembling squirrels and koalas.

As for the blood shrews, night gliders emerged from the caves as terrestrial forms called creepers. Just as far removed from the ancestral lizard-like form as the mammal-like furred shrews, these monstrous-looking creatures mostly resided in the blazing hot deserts of eastern Glicker, where they feasted on the blood of plents in the dark of night.

Bad luck would strike western Glicker as a minor meteor impact would wipe out the megafaunal shrews present there. However, as though it were foreshadowing, it was not long afterwards that an even bigger impact event would shake the entire planet.



The Ice Comet
Countless shrews would meet their end at the Somanian-Raptorian boundary, as a global impact winter collapsed the food chain and all species over 1 meter perished. This also included all xolagoba-grade furred shrews despite their smaller size, as they depended on trees for survival. However, shortly before the impact event, the more terrestrial joviglut had evolved, which was able to weather through the impact winter. Meanwhile in Glicker, creepers and small shroots also made it through mostly unscathed, though shroots would vanish from a local extinction event everywhere outside the wetlands where they became isolated by competitive pressure, thus furred shrews were almost completely extirpated from the landmass.

The joviglut went on to diversify all over Wright, forming the 'glut' evolutionary grade distinguished from their ancestors by a long tail and a bare, wet nose. As the Wright supercontinent broke up, they also produced multiple saber-toothed predatory forms, including the guloglut of Barlowe which resembled a saber-toothed wolverine and the Saberden of Jaydoh which had powerful forelimbs, as well as herbivorous forms like the whiskerpick and icicleback which were the first shrews to have whiskers.



Ice Age
When the ice age began, most blood shrews became extinct as it progressed, as they were cold-blooded and ill-suited to the changing climate. This pushed the evolution of the bubbleskin, a lukewarm-blooded blood shrew which resembles something like a theropodal gorgonopsid covered in bubble wrap. Meanwhile, in Dixon and Barlowe--what was previously known as Wright--the warm-blooded furred shrews had greater success, taking over the continent.

When the ice age worsened into a snowball event, all Shrews went extinct except for the whiskered shrews, the bubbleskins, the Desert Soriparasite (which remained isolated in its cave), the guloglut, and the wetland velishroots. When the ice receded, the guloglut died out. While Bubbleskins continued to diversify and thrive across different parts of the world, especially Drake and Vivus, the surviving whiskered 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.

Post-Thaw
Following the thaw, all surviving groups of shrews produced waves of diversity that, due to their disparate nature, requires them to be covered separately.



Blood Shrews: Bubbles and Lizards
Following the thaw, the bubbleskins--lukewarm-blooded, bipedal blood shrews--saw far greater success than their ancestors and split into two clades, the Drake bubbleskins of the north and the buoyskins of the south.

The Drake bubbleskins diversified into raptor-like forms, some megafaunal. This included the first blood shrew to regain the ability to feed on parts of their prey other than blood--the press-toothed bubbleskin, which accomplishes this by simply squeezing its prey with its jaws until its innards are liquified by pressure alone. Sprinting bubbleskins also regained this ability independently, with the far simpler method of extracting softer, easily-processed body parts.

Buoyskins were initially semi-aquatic, but in the Blargian a branch of them returned to living on land full-time as raptor-like predators. Initially exclusive to Vivus island, as it collided with Darwin they invaded the mainland for a time--at least, until they started being beaten back by argusraptor saucebacks, leaving their future up in the air.

Bubbleskins were not the only blood shrews still alive after the ice age, however. In the Darthian period, soriparasites abruptly emerged from the Rabid Sandstone Caves in the form of the Lazarus Soriparasite. The most anatomically primitive Shrew still extant, it produced several descendants that either continued specializing on a parasitic path or took the relatively free real estate of being "reptiles"--as unlike their main competitors in that area, the turtsnappers, they are pre-adapted for breeding on land. The more reptile-like soriparasites that ceased parasitic behavior are sometimes collectively called "sorites".



Whiskered Shrews: From Jaydoh to Conquest
As the ice thawed, whiskered shrews were isolated on Jaydoh island. Without influence from organisms on other landmasses, Jaydoh developed a unique assemblage of megafaunal shrews descended from the whiskerpick. There were two main native branches, the cheekhorns (which, as their name suggests, have horns on their cheeks) and the tams (which are armored).

A clade of semi-aquatic Shrews comparable to Terran beavers originated in Jaydoh and constructed floating nests to avoid their predators, the Jaydoh waxfaces (a clade of sauceback). They subsequently rafted across the ocean and spread to Dixon, Barlowe, and surrounding islands, and they didn't even actually succeed in escaping from the waxfaces because they learned to swim and hijack their nests. 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 happened, all furred shrews apart from descendants of the Marine Tamow and Beach Cheekhorn became extinct.

This leaves 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.

The tams of Dixon, descended from the Pickaxe Tamow, became lither and more traditionally mammal-like, even producing (terran) shrew-like forms--a morphological form that shrews had ironically never actually accomplished before. Dixon tams are difficult to categorize without paraphyly, but can be roughly sorted into basal nest-makers, predatory dog-like forms such as the tigmadar, and the neoshrews, which also contain the twintails--small predatory shrews with two tails.

The tams of Barlowe are generally more bulky, like their ancestors, with the exception of the lither, arboreal leemallas. They also produced predatory saber-toothed forms with retractable sickle claws. The more basal herbivorous grade was previously diverse, even producing a form which could make simple pottery from sand and urine to store and pickle fruit, but the Zealandia-esque sinking of Barlowe whittled them down significantly.

Some tams not only remained semi-aquatic but advanced their ability to construct their floating nests. They produced more intelligent otter-like forms, known as Tamjacks, which evolved to thrive in a now-sunken archipelago that surrounded Barlowe, though a branch of them also made it to Dixon. 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, shrews can be said to have conquered the world, as at least one species is present on even the most isolated islands. It has yet to be seen if the cosmopolitan status of this clade will last, however.

The original marine tamow remains extant, and has also more recently produced more basal offshoots, such as the Adorned Tamow, the Quillmow, and the Tamwodjir of the driftwood islands.

Shroots: Obscurity to Victory
The whiskered shrews were not the only furred shrews still extant after the snowball event, as miraculously shroots managed to ride through it all and emerge unscathed. However, similar to Earth's multituberculate mammals, the shroots were held in place within the wetlands by competitive pressure until the Huckian period, where a combination of climate factors and new innovations in predatory saucebacks reduced the pressure being exerted on them by neonodents. This caused shroots to almost abruptly emerge from the wetlands and reestablish themselves, even pushing out similarly-sized tams, revealing that they had undergone dramatic change in order to hold their ground against competition for so long.

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.

Types of Shrews
The relation between the main living groups of shrews is as follows:

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. Although most members of this group are pretty small, a few megafaunal species like the Short-Necked Shrew do exist.

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 closest living relatives of tams. Named after the horns that grow out of their cheeks, these shrews are large herbivores that generally resemble ungulates in appearance.

Modern shroots are a much earlier offshoot of furred shrews comparable to Earth's platypus in divergence. Unlike other furred shrews, their hind scapulae are still internal and they lack whiskers.

Extinct
†: Taxon is 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.

Earless furred shrews were basal furred shrews which lacked external ears and resembled therapsids. They were almost completely wiped out by the shrew plague, but a single species persisted on an island until it was wiped out by the gamma ray burst.

Stalking shrews were the earliest grade of furred shrews to have external ears. They differ from later grades in that they had straight spines and did not gallop. Shrotters are a part of this evolutionary grade, however the last species that resembled the ancestral stalking shrew died out as a result of the gamma ray burst.

Basal shroots were the earliest furred shrews which could gallop. They are also the last grade on the line to living furred shrews to retain the ancestral number of toes. They were largely wiped out by a series of local extinction events, but they survived in isolation via competitive pressure and eventually evolved into the visually similar but internally distinct modern shroots.

Xolagobas were a grade of furred shrew which were largely arboreal and had prominent incisors. They were the first polydactyl furred shrews. As they were entirely arboreal, they were wiped out by the ice comet impact event, which had killed all trees.

Gluts were the first furred shrews to have bare noses. They were smart and lemur-like, and were the first shrews to have dentition resembling that of modern groups.

Quilltails were the ancestors of cheekhorns. All non-cheekhorn quilltails became extinct as a result of the sinking of Jaydoh Island.

Blood Shrews
†: Taxon is extinct.

Extant
Crown-group soriparasites utilize an enlarged lower lip to help them suck blood from the wounds of their hosts. They are the only living blood shrews to still produce milk.

Bubbleskins are bipedal blood shrews with gorgonopsian-esque faces. Their skin is covered in bubble-like scales.

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.

Night gliders used their patagia to glide between hosts. The last true night glider died out as a result of its hosts being wiped by the Cave Plague.

Creepers were more terrestrial and hunted down hosts to vampirize. Creepers were largely wiped out by the snowball event, as they could not cope with the global ice conditions and the one species that managed to survive in a cave soon fell to the Golden Plague.

Basal soriparasites remained largely attached to their hosts and included some of the most specialized parasitic shrews. The last basal soriparasite was wiped out by the gamma ray burst.

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

Shrew lizards were ectothermic, superficially monitor lizard-like predatory shrews. This grade of shrew was wiped out by the shrew plague.

Were shrews were naked mesothermic shrews which were the ancestors of furred shrews. This grade of shrew was wiped out by the shrew plague.

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).