The Zoochat Photographic Guide to Rodents: part one

Chlidonias

Chlidonias

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Rodents dominate the Class Mammalia. There are around 2400 species of rodents in total, housed in over 500 genera. About 42% of all mammal species are included within the Order Rodentia - there are twice as many rodent species as there are bat species. The general structure of the Order has remained fairly constant since the 1800s, the most major change being that the lagomorphs (rabbits, hares, and pikas) used to be included within the group until the start of the 1900s.

Rodentia has been separated into three Suborders for almost 200 years - Myomorpha ("mouse-like"), Sciuromorpha ("squirrel-like"), and Hystricomorpha ("porcupine-like") - distinguished by the jaw structures. More recently, two further small Suborders have been separated from the Sciuromorpha - Anomaluromorpha (less than ten species) and Castorimorpha (about 100 species). These five Suborders are the currently-accepted divisions for most taxonomists today, although being taxonomy there are various other positions available for how to arrange the Order.

As may be expected, the number of individual species in Rodentia has crept continuously upwards due to regular discoveries of unknown species and to genetics-based splitting (since 1980 about 600 new species have been added), but the number of Families has remained pretty steady, at between 30 and 35 - even if the exact placement of those Families within the Suborders hasn't always been agreed upon!

I would encourage a reading of the Rodentia page on the website for Wilson and Reeder's Mammal Species of the World, which goes into much more detail about the taxonomy and history than I can give here: Mammal Species of the World - Browse: RODENTIA


As always, thanks are given to all the hard-working photographers who make these threads (and the future threads) possible. The list of members whose photos have been used in this thread is here on page 13 - The Zoochat Photographic Guide to Rodents: part one
 
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I am covering Rodentia across two threads. Part one (this thread) will include four of the five Suborders, with about 740 species in total. Part two will be just for the Myomorpha, with about 1680 species - that thread is here: The Zoochat Photographic Guide to Rodents: part two.


Part one:
Suborder Sciuromorpha (c.330 spp)
Suborder Anomaluromorpha (9 spp)
Suborder Castorimorpha (c.100 spp)
Suborder Hystricomorpha (c.300 spp)

Part two:
Suborder Myomorpha (c.1680 spp)


There proved to be a fairly good representation of photographs for part one - over half the genera are represented (90 out of c.158), and about a quarter of the total species (250 or 252] out of c.740) - but part two was less successful, with the long strings of listed species of rats and mice only having intermittent photos to break the monotony. Of the c.1680 species of c.346 genera in Myomorpha, only 213 species from 105 genera have photographs.


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The presentation of Families as they will appear in these threads are as follows.


Suborder SCIUROMORPHA
(c.330 spp in 70 genera, of which 157 spp from 47 genera are depicted here)

Family Aplodontiidae - Sewellel or Mountain Beaver (1 sp - depicted as a museum specimen)
Family Sciuridae - Squirrels (c.300 spp in 60 genera - 148 spp from 40 genera are depicted)
Family Gliridae - Dormice (c.30 spp in 9 genera - 8 spp from 6 genera are depicted)


Suborder ANOMALUROMORPHA
(9 spp in 4 genera, of which four species from two genera are depicted here)

Family Anomaluridae - Anomalures or Scaly-tailed Squirrels (7 spp in 3 genera - two species from one genus are depicted)
Family Pedetidae - Springhares (2 spp in one genus - both species are depicted)


Suborder CASTORIMORPHA
(c.100 spp in 12 genera, of which 16 spp from 6 genera are depicted here)

Family Castoridae - Beavers (2 spp in 1 genus - both species are depicted)
Family Geomyidae - Pocket Gophers (c.35-40 spp in 6 genera - only 4 spp from 2 genera are depicted)
Family Heteromyidae - Kangaroo Rats and Kangaroo Mice (c.60 spp in 5 genera - only 10 spp from 3 genera are depicted)


Suborder HYSTRICOMORPHA
(c.300 spp in 72 genera, of which only 73-75 spp from 35 genera are depicted here)

Family Diatomyidae / Laonastidae - Laotian Rock Rat (1 sp - not depicted)
Family Ctenodactylidae - Gundis (5 spp in 4 genera - two species from two genera are depicted)
Family Bathyergidae - Blesmols or African Mole Rats (c.25 spp in 6 genera - 8 spp from 4 genera are depicted)
Family Hystricidae - Old World Porcupines (11 spp in 3 genera - 10 spp from 2 genera are depicted)
Family Petromuridae - Dassie Rat (1 sp - depicted)
Family Thryonomyidae - Cane Rats (2 spp in 1 genus - one species is depicted)
Family Erethizontidae - New World Porcupines (c.17 spp in 3 genera - 12 spp from all 3 genera are depicted)
Family Chinchillidae - Chinchillas and Viscachas (7 spp in 3 genera - 4 spp from all 3 genera are depicted)
Family Dinomyidae - Pacarana (1 sp - depicted)
Family Caviidae - Cavies (c.20 spp in 6 genera - 11 or 12 spp from all 6 genera are depicted)
Family Dasyproctidae - Agoutis (c.13 spp in 2 genera - 8 or 9 spp from both genera are depicted)
Family Cuniculidae - Pacas (2 spp in 1 genus - both are depicted)
Family Ctenomyidae - Tuco-tucos (c.65 spp in 1 genus - 3 spp are depicted)
Family Octodontidae - Octodonts (14 spp in 8 genera - 2 spp from 2 genera are depicted)
Family Abrocomidae - Chinchilla Rats (c.10 spp in 2 genera - one species is depicted)
Family Echimyidae - New World Spiny Rats (c.90 spp in 21 genera - 4 spp from 3 genera are depicted)
Family Myocastoridae - Coypu (1 sp - depicted)
Family Capromyidae - Hutias (c.13 spp in 5 genera - 2 spp from 2 genera are depicted)


Suborder MYOMORPHA
(c.1680 spp in c.346 genera, of which only 213 spp from 105 genera are depicted here): see The Zoochat Photographic Guide to Rodents: part two

Family Dipodidae - Jerboas and Jumping Mice (c.50 spp in 16 genera - 14 spp from 8 genera are depicted)
Family Platacanthomyidae - Spiny Dormice (3 spp in 2 genera - one species is depicted)
Family Spalacidae - Mole-Rats and Bamboo Rats (c.30-40 spp in 6 genera - 7 spp from 4 genera are depicted)
Family Calomyscidae - Mouse-like Hamsters (8 spp in one genus - one species is depicted)
Family Nesomyidae - Madagascan and African Rats and Mice (c.65-70 spp in 21 genera - 17 spp from 8 genera are depicted)
Family Cricetidae - Voles, Hamsters, and New World Rats and Mice (c.700 spp in c.140 genera - 68 spp from 38 genera are depicted)
Family Muridae - Old World or "True" Mice and Rats, Gerbils, and Spiny Mice (c.810 spp in c.160 genera - 105 spp from 45 genera are depicted)
 
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Suborder SCIUROMORPHA


There are three Families within this Suborder, containing about 330 species in total: Aplodontiidae (the Sewellel or Mountain Beaver), Sciuridae (squirrels), and Gliridae (dormice).


Gliridae has in the past been more commonly included within the Myomorpha (rats and mice), but it is now considered that the "myomorph" jaw structure of dormice is convergent and that they are actually sciuromorphs. However there are also suggestions that Gliridae is paraphyletic and that some members of the Family belong instead in Anomaluromorpha.


The Suborders Anomaluromorpha (anomalures and springhares) and Castorimorpha (beavers, gophers, and kangaroo rats) have also been placed in Sciuromorpha in the past.
 
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APLODONTIIDAE
Aplodontids

One living species


This Family has an extensive fossil history from the Oligocene onwards, from across the entire Northern Hemisphere. Wikipedia lists 22 fossil genera in the Family. Today there is a sole living species, the Sewellel or Mountain Beaver, which has a limited distribution in the western USA. Despite the common name of the extant species, they are a sister group to squirrels and not closely related to beavers at all.


Sewellel or Mountain Beaver Aplodontia rufa
Seven subspecies: californica, humboldtiana, nigra, pacifica, phaea, rainieri, rufa


The photo used below is of a taxidermy specimen. The only other photos depicting the species in the Zoochat galleries are an archive ZSL photo of a live animal (not used here because it was not taken by a member - Mountain Beaver or Sewellel (Aplodontia rufa) | ZooChat) and a couple of photos of an exhibit display which include a model Sewellel (Secrets of the Forest | ZooChat).


Photo by @Ituri at the Conner Museum of Natural History, Washington State University (USA)

The museum label gives the locality as "Western Washington" which, if indicating the provenance of the specimen, would make this the nominate subspecies rufa.

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Sewellel (museum specimen) | ZooChat
 
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Family SCIURIDAE
Squirrels

About 300 species in 60 genera, of which 148 species from 40 genera are depicted here.


The Family Sciuridae is divided into five subfamilies, as follows:


Ratufinae (giant squirrels) - four species in a single genus (Ratufa). All four species are depicted here.

Sciurillinae (Neotropical Pigmy Squirrel) - one species, in the genus Sciurillus; not depicted here.

Sciurinae - about a hundred species in twenty genera, in two Tribes:

Sciurini (tree squirrels) with about 38 species in five genera (Microsciurus, Rheithrosciurus, Sciurus, Syntheosciurus, Tamiasciurus). There are twenty species depicted here, from three genera: Microsciurus, Sciurus, Tamiasciurus.

Pteromyini (flying squirrels) with about sixty species in fifteen genera (Aeretes, Aeromys, Belomys, Biswamoyopterus, Eoglaucomys, Eupetaurus, Glaucomys, Hylopetes, Iomys, Petaurillus, Petaurista, Petinomys, Pteromys, Pteromyscus, Trogopterus). There are twenty species depicted here, from eight genera: Aeretes, Aeromys, Glaucomys, Hylopetes, Iomys, Petaurista, Petinomys, Pteromys.

Callosciurinae (Asian squirrels) - about seventy species in fourteen genera (Callosciurus, Dremomys, Exilisciurus, Funambulus, Glyphotes, Hyosciurus, Lariscus, Menetes, Nannosciurus, Prosciurillus, Rhinosciurus, Rubrisciurus, Sundasciurus, Tamiops). There are 36 species depicted here, from nine genera: Callosciurus, Dremomys, Exilisciurus, Funambulus, Lariscus, Menetes, Prosciurillus, Sundasciurus, Tamiops.

Xerinae (ground squirrels) - about 125 species in twenty-four genera, in three Tribes:

Xerini (African ground squirrels) with six species in three genera (Atlantoxerus, Spermophilopsis, Xerus). There are four species depicted here, from two genera: Atlantoxerus and Xerus.

Protoxerini (African tree squirrels) with thirty species in six genera (Epixerus, Funisciurus, Heliosciurus, Myosciurus, Paraxerus, Protoxerus). There are ten species depicted here, from three genera: Funisciurus, Heliosciurus, Paraxerus.

Marmotini (Holarctic ground squirrels) with ninety species in fifteen genera (Ammospermophilus, Callospermophilus, Cynomys, Eutamias, Ictidomys, Marmota, Neotamias, Notocitellus, Otospermophilus, Poliocitellus, Sciurotamias, Spermophilus, Tamias, Urocitellus, Xerospermophilus). There are fifty-four species depicted here, from fourteen genera. The only genus not yet represented is Notocitellus.


All the genera above are listed alphabetically under their Subfamily / Tribe, and they will be presented in the following posts in that same order.
 
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The subfamily Ratufinae contains a single genus, with just four species.



Ratufa
Four species, all of which are represented in the Zoochat galleries.


Cream-coloured Giant Squirrel Ratufa affinis
Nine subspecies: affinis, bancana, baramensis, bunguranensis, cothurnata, ephippium, hypoleucos, insignis, polia

The common name above is the most widely-used but I prefer to call them Variable Giant Squirrels because, while the subspecies in the mainland areas of southeast Asia (southern Thailand and Peninsular Malaysia) is always solidly-coloured, on Borneo they come in multi-colour patterns and hence "Cream-coloured" is not at all appropriate.


Photo by @devilfish at Pata Zoo, Thailand (mainland subspecies affinis)

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Cream-coloured giant squirrel, June 2016 | ZooChat


Photo by @devilfish at Lok Kawi Wildlife Park, Sabah (north Bornean subspecies baramensis - the northern part of this subspecies' range is split as sandakanensis by various authors, in which case the animal pictured here is sandakanensis)

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Cream-coloured giant squirrel, June 2016 | ZooChat


Black or Bicoloured Giant Squirrel Ratufa bicolor
Up to twenty subspecies have been recognised in the past, but currently only about half that are considered valid (although possibly a species complex): angusticeps, bicolor, condorensis, felli, gigantea, hainana, leucogenys, melanopepla, palliata, phaeopepla, smithi


Some of the named subspecies have discreet ranges (e.g. bicolor on Java and Bali, condorensis on Vietnam's Con Dao islands, felli in a small area of northern Myanmar, hainana on Hainan Island, and palliata on Sumatra), but for the others it is difficult working out where subspecies are supposed to be distributed. For example, Squirrels of the World by Thorington et al gives exactly the same distribution for angusticeps, leucogenys, melanopepla and phaeopepla, namely "Myanmar and Thailand south through peninsular Malaysia and the Natuna Islands (Indonesia)", and says that these subspecies are virtually indistinguishable from one another - which obviously calls into question why they are even still considered valid. There are a number of good photos in the Zoochat galleries of Black Giant Squirrels from Malaysia and Thailand but, with little available for me to say what's what, I have used only one of them (from Malaysia) simply as a comparison for the photos of known subspecies (bicolor, condorensis, gigantea, smithi).


Photo by @Tomek at Wroclaw Zoo, Poland (Javan subspecies bicolor, showing the distinctive colouration in comparison to other subspecies)

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Javan black giant squirrel (Ratufa bicolor bicolor) | ZooChat


Photo by @Maguari at Saigon Zoo, Vietnam (Con Dao subspecies condorensis)

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Condao Black Giant Squirrel at Saigon Zoo, 16/03/12 | ZooChat


Photo by @Chlidonias in the wild, Vietnam ("northern" subspecies gigantea)

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Black Giant Squirrel (Ratufa bicolor) | ZooChat


Photo by @LaughingDove in the wild, Vietnam (south Vietnamese subspecies smithi)

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Black Giant Squirrel - Mount Lang Biang | ZooChat


Photo by @Toki in the wild, Penang Island (Malaysia) - this insular population was formerly treated as a distinct subspecies, R. b. penangensis.

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Black Giant Squirrel (Ratufa bicolor) - ZooChat


Photo by @Chlidonias at Melaka Zoo, Malaysia (one of the "southern" subspecies, used here as comparison to the known subspecies photos above)

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black giant squirrel (Ratufa bicolor) | ZooChat


Malabar or Indian Giant Squirrel Ratufa indica
Four subspecies: centralis, dealbata, indica, maxima


Photo by @Chlidonias in the wild, India (subspecies indica)

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Malabar Giant Squirrel (Ratufa indica) | ZooChat


Photo by @Chlidonias in the wild, India (subspecies maxima)

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Malabar Giant Squirrel (Ratufa indica) | ZooChat


Grizzled or Sri Lankan Giant Squirrel Ratufa macroura
Three subspecies: dandolena, macroura, melanochra


Photo by @Goura at Leipzig Zoo, Germany (Sri Lankan Dry Zone subspecies dandolena)

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Sri Lankan giant squirrel | ZooChat


Photo by @Chlidonias in the wild, India (this isolated Indian population is treated as being of the same subspecies - dandolena - as is found in the Sri Lankan Dry Zone)

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Grizzled Giant Squirrel (Ratufa macroura) | ZooChat


Photo by @Chlidonias in the wild, Sri Lanka (Wet Zone subspecies melanochra)

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Sri Lankan Giant Squirrel (Ratufa macroura melanochra) | ZooChat
 
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The subfamily Sciurillinae contains a single genus, with only one species currently recognised.



Sciurillus
One species.


Neotropical Pigmy Squirrel Sciurillus pusillus
Three subspecies recognised - glaucinus, kuhlii, pusillus - although this could be a species complex.


There are no photos of this species in the Zoochat galleries.
 
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Chlidonias said:
Grizzled or Sri Lankan Giant Squirrel Ratufa macroura
Three subspecies: dandolena, macroura, melanochra
Click to expand...

A very nice species, and one which I fear will soon be eligible for my "Species We Have Lost" thread given the fact that in the last decade all but one of the seven holders of the taxon have lost the species, and the final holder has not successfully bred their animals which are now quite old.
 
The subfamily Sciurinae contains about a hundred species in twenty genera, divided between two Tribes.


The members of the Tribe Sciurini could be termed "typical squirrels", containing as they do the type genus Sciurus. There are about 38 species in five genera: Microsciurus, Rheithrosciurus, Sciurus, Syntheosciurus, Tamiasciurus.

Twenty species are depicted here, from three genera: Microsciurus, Sciurus, Tamiasciurus.


The Tribe Pteromyini (or Petauristini) contains all the flying squirrels - gliding behaviour seems to have evolved only in this group of squirrels. Formerly this group was separated as a subfamily (Pteromyinae or Petauristinae). Most species come from Asia. There are about sixty species in fifteen genera: Aeretes, Aeromys, Belomys, Biswamoyopterus, Eoglaucomys, Eupetaurus, Glaucomys, Hylopetes, Iomys, Petaurillus, Petaurista, Petinomys, Pteromys, Pteromyscus, Trogopterus.

Twenty species are currently depicted here, from eight genera: Aeretes, Aeromys, Glaucomys, Hylopetes, Iomys, Petaurista, Petinomys, Pteromys.



An interesting distributional observation is that the "typical" tree squirrels of Sciurini are almost all from the Northern Hemisphere and South America (only one species is found in southeast Asia), whereas the flying squirrels of Pteromyini are almost the complete opposite. There are three species of flying squirrel in North America, one in Europe, and a handful in eastern and southern Asia, but there are almost forty species in the forests of southeast Asia.
 
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Microsciurus
Four species are normally listed, but the taxonomy is complicated. For example, Patton et al (Mammals of South America) recognise eleven species by splitting off several subspecies.



The "standard" four species with their recognised subspecies are as follows (in order of distribution, north to south):

Central American Dwarf Squirrel Microsciurus alfari
Four to six subspecies: alfari, alticola, browni, fusculus, septentrionalis, venustulus
Distributed from Nicaragua to northern Colombia.

Western Dwarf Squirrel Microsciurus mimulus
Three subspecies: boquetensis, isthmius, mimulus
Distributed in the highlands of western Panama and in the lowlands of Darien (far-eastern Panama) to northwest Ecuador and southwest Colombia.

Amazon Dwarf Squirrel Microsciurus flaviventer
Eight subspecies: flaviventer, napi, otinus, peruanus, rubrirostris, sabanillae, similis, simonsi
Found in northwest South America.

Santander Dwarf Squirrel Microsciurus santanderensis
Monotypic
Found only in the Santander region of Colombia.




If eleven species are considered valid then they are as follows (in order of distribution, north to south):

Central American Dwarf Squirrel Microsciurus alfari
Four subspecies: alfari, alticola, browni, septentrionalis (the subspecies fusculus from Colombia is far south of the species' range and so in this case would be placed under Microsciurus similis)
Distributed from Nicaragua to southwest Panama.

Panama Dwarf Squirrel Microsciurus venustulus
Monotypic (split from M. alfari)
Restricted to central Panama.

Boquete Dwarf Squirrel Microsciurus boquetensis
Monotypic (split from M. mimulus)
Restricted to the highlands of western Panama.

Isthmian Dwarf Squirrel Microsciurus isthmius
Monotypic (split from M. mimulusi)
Restricted to Darien (far-eastern Panama) and northwest Colombia.

Rufous-breasted Dwarf Squirrel Microsciurus similis
Monotypic, or with one additional subspecies (fusculus, transferred over from M. alfari) (split from M. flaviventer)
Restricted to western Colombia, west of the Andes.

Simon's Dwarf Squirrel Microsciurus simonsi
Monotypic (split from M. flaviventer)
Restricted to Ecuador, west of the Andes.

White-eared Dwarf Squirrel Microsciurus otinus
Monotypic (split from M. flaviventer)
Restricted to Colombia, west of the Andes.

Santander Dwarf Squirrel Microsciurus santanderensis
Monotypic
Found only in the Santander region of Colombia.

Western Dwarf Squirrel Microsciurus mimulus
Monotypic
Now restricted to northwest Ecuador and southwest Colombia (west of the Andes) after the splitting off of M. boquetensis and M. isthmius.

Sabanilla Dwarf Squirrel Microsciurus sabanillae
Monotypic (split from M. flaviventer)
Found in Ecuador and northwest Peru.

Amazon Dwarf Squirrel Microsciurus flaviventer
Monotypic
Distributed through western Amazonia.




Contrasting completely with this is a paper published in 2020 re-evaluating the American Sciurinae (Museomics of tree squirrels: a dense taxon sampling of mitogenomes reveals hidden diversity, phenotypic convergence, and the need of a taxonomic overhaul | BMC Evolutionary Biology) wherein the authors divide Microsciurus into three genera:

Microsciurus
Microsciurus alfari (including M. venustulus)
Microsciurus "species 1" (a Colombian form previously included within M. mimulus)

Leptosciurus
Leptosciurus mimulus
Leptosciurus pucheranii (the study found that Sciurus pucheranii was not actually a single variable species but rather two entirely different lineages, and hence they placed one form (the nominate subspecies pucheranii) here amongst the dwarf squirrels and the remaining subspecies they renamed as Hadrosciurus ignitus)
Leptosciurus similis
Leptosciurus otinus
Leptosciurus boquetensis
Leptosciurus isthmius

"Microsciurus"
"Microsciurus" sabanillae
"Microsciurus" "species 2" (an undescribed form from Peru and Brazil, variously included in Microsciurus or Syntheosciurus)
"Microsciurus" flaviventer

(Note that M. santanderensis and M. simonsi are not included in the three genera above because they were amongst the few species not sampled genetically in this study).


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Whichever treatment is followed, only one species is currently represented by photos in the Zoochat galleries.


Central American Dwarf Squirrel Microsciurus alfari
Four to six subspecies: alfari, alticola, browni, fusculus, septentrionalis, venustulus
If the species is split in two, then venustulus becomes a full monotypic species; and the subspecies fusculus is probably best placed under Microsciurus similis.


Photo by @ralph in the wild, Costa Rica (subspecies browni)

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Squirrel (ID?) | ZooChat


Photo by @Giant Eland in the wild, Costa Rica (I think this must be the subspecies alfari)

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Alfaro's Pygmy Squirrel (Microsciuris alfari) | ZooChat


Photo by @Newzooboy in the wild, Costa Rica (subspecies alticola)

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Alfaro's Pygmy Squirrel - ZooChat
 
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Rheithrosciurus
One species

This genus is notable for being the sole representative of Sciurini in southeast Asia (all other genera in the Tribe are from the Northern Hemisphere and the Neotropics). It is endemic to Borneo, but its presence there is a biogeographical mystery as there are no connecting fossil forms for the region.



Tufted Ground Squirrel Rheithrosciurus macrotis
Monotypic


There are no photos of this species in the Zoochat galleries.
 
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Sciurus
About twenty-nine species, seventeen of which are represented in the Zoochat galleries.

Revisions of this genus by various authors have split it into multiple genera (all the Northern Hemisphere species have been kept in Sciurus, but almost all the Neotropical species have been split amongst what were formerly subgenera). There is disagreement as to which species belong in which genera, however, so I have retained them all here under Sciurus.


Below is a run-through of the split genera and combinations of species.

Sciurus, as mentioned above, normally retains all the Northern Hemisphere species as well as some Neotropical species from Central America, with sixteen species in total: aberti, alleni, anomalus, arizonensis, aureogaster, carolinensis, colliaei, griseus, lis, meridionalis, nayaritensis, niger, oculatus, variegatoides, vulgaris, yucatanensis.

Notosciurus usually would contain three to six species: granatensis, ignitus, deppei, pucheranii, richmondi and sanborni. Patton et al (in Mammals of South America) treat ignitus as a subspecies of pucheranii, and sanborni as a synonym of N. pucheranii boliviensis; they also seem to include deppei as a subspecies of pucheranii. The Nicaraguan endemic richmondi may be treated as a subspecies of granatensis by some authors also.

Gerlinguetus may be inclusive of the Notosciurus species (as listed above) but if those species are split off then only two or three remain in Guerlinguetus. The two usually listed are aestuans and gilviventris but, to make it more complicated, Patton et al treat gilviventris as a subspecies of aestuans, and they then split off a different species (brasiliensis) from aestuans. In this thread I keep aestuans and gilviventris as separate species, and include Patton's brasiliensis within aestuans - but it should be obvious that the taxonomy of Neotropical squirrels is extremely poorly-studied and many "species" are probably complexes.

Hadrosciurus would usually include four species: flammifer, igniventris, pyrrhinus and spadiceus. Patton et al put flammifer as a subspecies of igniventris.

Urosciurus may be used for two of the above species (igniventris - presumably also flamifer - and spadiceus), leaving only pyrrhinus in the genus Hadrosciurus.

Simosciurus would contain a single species, stramineus. Patton et al recognise two species (nebouxii and stramineus) by splitting.


A paper by de Abreu-Jr. et al, published in 2020, made things even more splitty and complicated (Museomics of tree squirrels: a dense taxon sampling of mitogenomes reveals hidden diversity, phenotypic convergence, and the need of a taxonomic overhaul | BMC Evolutionary Biology). They retained only three species in the genus Sciurus and divided all the rest between nine genera:

Sciurus for anomalus, lis and vulgaris.
Hesperosciurus for griseus and aberti.
Parasciurus for arizonensis, nayaritensis, niger, alleni and oculatus.
Neosciurus for carolinensis.
Syntheosciurus for granatensis (this was an existing genus to which they moved one Sciurus species; and they include richmondi in granatensis).
Echinosciurus for aureogaster, colliaei, deppei, yucatanensis and variegatoides.
Leptosciurus for pucheranii (this was a genus they created to house some of the Microsciurus species, and to which they moved one Sciurus species).
Simosciurus for nebouxii and stramineus.
Guerlinguetus for aestuans and brasiliensis.
Hadrosciurus for igniventris, pyrrhinus, ignitus and spadiceus.
 
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Abert's Squirrel Sciurus aberti
Six subspecies: aberti, barberi, chuscensis, durangi, ferreus, kaibabensis


First two photos below by @Giant Eland in the wild, Arizona (USA) (subspecies aberti)

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Abert's squirrel or the tassel-eared squirrel (Sciurus aberti aberti) - ZooChat

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Abert's squirrel or the tassel-eared squirrel (Sciurus aberti aberti) - ZooChat


Photo by @carlos55 at the American Museum of Natural History, USA (subspecies kaibabensis) (taxidermy specimen)

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albert´s squirrel | ZooChat


Brazilian or Guianan Squirrel Sciurus aestuans
Note: may be placed in the separated genus Guerlinguetus.

Subspecies are a complete mess, with at least twelve being used: aestuans, alphonsei, brasiliensis, garbei, georgihernandezi, henseli, ingrami, macconnelli, paraensis, poaiae, quelchii, venustus

Note: Patton et al split this into two species in Mammals of South America, namely the Guianan Squirrel G. aestuans (with two subspecies, aestuans and gilvigularis - the latter otherwise split as a full species, the Yellow-throated Squirrel) and the Brazilian Squirrel G. brasiliensis (with three subspecies - brasiliensis, ingrami, and paraensis; brasiliensis is apparently an older name than ingrami and thus has precedence as the specific name). In the 2020 paper by de Abreu-Jr. (linked in the introductory post for the genus Sciurus) the species is also split, but into four species - "aestuans" A, B, and C, and brasiliensis.

Given the taxonomic issues I have retained both aestuans and brasiliensis as a single species, although both are depicted below.


Photo by @Giant Eland in the wild, Brazil (labelled as Brazilian Squirrel Sciurus aestuans)

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Brazilian squirrel (Sciurus aestuans) - ZooChat


Photo by @Therabu in the wild, Brazil (labelled as Ingram's Squirrel Sciurus ingrami)

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Ingram's squirrel (Sciurus ingrami) - ZooChat


Persian or Caucasian Squirrel Sciurus anomalus
Three subspecies: anomalus, pallescens, syriacus

None of the photos in the Zoochat galleries are labelled to subspecies, but probably all three subspecies are represented (definitely pallescens, which has photos of wild animals in Iran).


Photo by @PossumRoach at Karatay Municipal Zoo, Turkey (probably the subspecies anomalus, which is found in Turkey)

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Caucasian squirrel from Karatay Municipal Zoo - ZooChat


Photo by @fofo in the wild, Iran (subspecies pallescens)

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wild Persian squirrels - ZooChat


Photo by @alexkant at Meir Segals Garden University Zoo, Israel (probably the subspecies syriacus, which is found in Israel and neighbouring countries)

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Persian squirrel/ Sciurus anomalus | ZooChat


Arizona Grey Squirrel Sciurus arizonensis
Three subspecies: arizonensis, catalinae, huachuca (although also treated as monotypic by some authors - the three populations are separate from one another).


Photo by @Ituri in the wild, USA (subspecies huachuca)

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Arizona Gray Squirrel | ZooChat


Photo by @Arizona Docent in the wild, USA (subspecies huachuca - these two photos were taken at the same location, at Madera Canyon in Arizona)

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Arizona gray squirrel - ZooChat


Mexican Grey Squirrel or Red-bellied Squirrel Sciurus aureogaster
Two subspecies: aureogaster, nigrescens

This is a species with rather variable colouration (not related to subspecies nor particularly to distribution).


Photo by @Giant Eland in the wild, Mexico (subspecies nigrescens)

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2013 Chapultepec Zoo | ZooChat


Eastern Grey Squirrel Sciurus carolinensis
Five subspecies are currently recognised (carolinensis, extimus, fuliginosus, hypophaeus, pennsylvanicus) but they intergrade and may not all be valid. Numerous other subspecies have been recognised in the past.


Photo by @Ituri in the wild, Missouri (USA) (subspecies carolinensis)

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Southern Gray Squirrel | ZooChat


Photo by @Ituri in the wild, Florida (USA) (South Florida subspecies extimus)

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Florida Gray Squirrel | ZooChat


Photo by @Ituri in the wild, Minnesota (USA) (northern subspecies hypophaeus)

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Minnesota Gray Squirrel | ZooChat


Photo by @Giant Eland in the wild (in the grounds of the Smithsonian National Zoo, Washington DC), USA (subspecies pennsylvanicus)

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Eastern Gray Squirrel (Sciurus carolinensis) | ZooChat


Photo by @Newzooboy in the wild, Canada (melanistic form of the subspecies pennsylvanicus (introduced in this locality))

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Black Squirrel - Nov 2014 | ZooChat
 
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Red-tailed Squirrel Sciurus granatensis
Note: may be placed in one or other separated genera, Notosciurus or Guerlinguetus. In complete contrast, a 2020 study by de Abreu-Jr. et al (linked in the introduction post earlier for the genus Sciurus) places this species in the genus Syntheosciurus with Bangs' Mountain Squirrel S. brochus, which seems unlikely - given the ubiquitous confusion over identifications of S. brochus one might suggest that their genetic samples were misidentified.

Thirty-two subspecies are listed in Wilson and Reeder's Mammal Species of the World: agricolae, bondae, candelensis, carchensis, chapmani, chiriquensis, chrysuros, ferminae, gerrardi, granatensis, griseimembra, griseogena, hoffmanni, imbaburae, llanensis, manavi, maracaibensis, meridensis, morulus, nesaeus, norosiensis, perijae, quindianus, saltuensis, soederstroemi, splendidus, sumaco, tarrae, valdiviae, variabilis, versicolor, zuliae

In contrast, Patton et al's Mammals of South America recognise only six subspecies: chapmani, chrysuros, granatensis, hoffmanni, morulus, nesaeus

It is likely to actually be a species complex.

There are surprisingly few photos in the Zoochat galleries. All but one are of captive animals, and of those captive animals only the European ones are labelled as to subspecies (the Central American hoffmanni). Because of the confusing taxonomy and extreme variability of this species I have included additional photos of (unspecified) different forms below.


Photo by @vogelcommando at De Evenaar - Etten-Leur, Netherlands (subspecies hoffmanni)

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Red-tailed squirrel Ssp Hoffmanni | ZooChat


Photo by @Giant Eland at Parque Jaime Duque, Colombia (this colour form appears to be a match for that described in Patton et al as being common in Colombia's Sierra Nevada de Santa Marta range, under their (lumped) S. g. granatensis)

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Parque Jaime Duque 2012 | ZooChat


Photo by @Giant Eland at Parque Jaime Duque, Colombia (presumably one of the lowland colour forms from Colombia, which would be included under granatensis by Patton et al)

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Parque Jaime Duque 2012 | ZooChat


Western Grey Squirrel Sciurus griseus
Three subspecies: anthonyi, griseus, nigripes


Photo by @Giant Eland in the wild, USA (subspecies griseus)

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western gray squirrel (Sciurus griseus) - ZooChat


Bolivian Squirrel Sciurus ignitus
Note: may be placed in one or other separated genera, Notosciurus or Guerlinguetus.

Five subspecies: argentinius, boliviensis, cabrerai, ignitus, irroratus. May be a species complex.

In Mammals of South America by Patton et al the Bolivian Squirrel is placed as a subspecies of the Andean Squirrel S. pucheranii. In the 2020 study by de Abreu-Jr. referenced earlier, S. pucheranii was found to belong to a genus of dwarf squirrels (Microsciurus, but split as Leptosciurus in that paper), and to not be related to S. ignitus.


Photo by @devilfish at Santa Cruz Zoo, Bolivia (there are two subspecies in Bolivia - boliviensis and ignitus - but all the subspecies in this squirrel are based on distribution and not on physical differences)

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Bolivian squirrel, March 2016 | ZooChat


Japanese Squirrel Sciurus lis
Monotypic


Photo by @Giant Eland at Inokashira Park Zoo, Japan (summer coat)

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Japanese squirrel (Sciurus lis) | ZooChat


Both photos below by @Chlidonias at Inokashira Park Zoo, Japan (winter coat, in two colour forms)

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Japanese Squirrel (Sciurus lis) - ZooChat

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Japanese Squirrel (Sciurus lis) - ZooChat
 
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Mexican Fox Squirrel Sciurus nayaritensis
Three subspecies: apache, chiricahuae, nayaritensis


Photo by @Giant Eland in the wild, USA (subspecies chiricahuae)

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Mexican fox squirrel (Sciurus nayaritensis) - ZooChat


Photo by @branta68 in the wild, USA (also the subspecies chiricahuae)

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chiracuahua fox squirrel | ZooChat


Eastern Fox Squirrel Sciurus niger
Ten subspecies: avicennia, bachmani, cinereus, limitis, ludovicianus, niger, rufiventer, shermani, subauratus, vulpinus


Photo by @Maguari in the wild, USA (subspecies avicennia - Big Cypress Fox Squirrel)

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Big Cypress Fox Squirrel, Western Everglades/Big Cypress, October 2013 | ZooChat


Photo by @Pleistohorse in the wild, USA (subspecies limitis? - Texas Fox Squirrel)

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Fox Squirrel - Texas | ZooChat


Photo by @Giant Eland in the wild, USA (subspecies rufiventer - Western Fox Squirrel)

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2013: Peoria Zoo | ZooChat


Photo by @Ituri in the wild, USA (subspecies shermani - Sherman's Fox Squirrel)

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Sherman’s Fox Squirrel | ZooChat


Southern Amazon Red Squirrel Sciurus spadiceus
Note: may be placed in one or other separated genera, Urosciurus or Hadrosciurus.
Three subspecies: spadiceus, steinbachi, tricolor


Photo by @Giant Eland in the wild (subspecies steinbachi)

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southern Amazon red squirrel (Sciurus spadiceus) - ZooChat


Guayaquil Squirrel Sciurus stramineus
Note: may also be placed in the separated genus Simosciurus.

Variously treated as being either monotypic or with up to four subspecies (guayanus, nebouxii, stramineus, zarumae). In Mammals of South America by Patton et al the species is split into two monotypic species, with S. stramineus (including guayanus) being found in northern Peru and extreme south Ecuador, and S. nebouxii (including zarumae) in central Ecuador. Their justification is based mainly on colouration, in particular that the former (stramineus) has a prominent white nuchal patch and nebouxii supposedly does not. Other authors consider this difference to be a simple distribution-cline. This species appears to be really variable in colouration as the following photos show.


Photo by @Giant Eland in the wild, Lima (Peru). This is an introduced population well south of the natural range, and is named as being S. stramineus (rather than the possible split species S. nebouxii) by Patton et al.

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2013 Las Leyendas | ZooChat


Photo by @David Matos Mendes - also from the introduced Lima population.

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Guayaquil squirrel - Lima - ZooChat


Photo by @Giant Eland at Quito Zoo, Ecuador. Note the very prominent white nuchal patch, which according to Patton et al would make this S. stramineus (rather than their S. nebouxii). Quito is in northern Ecuador, but this may be a specimen from the far south of the country rather than being the Central Ecuadorean "S. nebouxii"

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Guayaquil squirrel (Sciurus stramineus) - ZooChat
 
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