| Supplementary Information
Table 1. Comparison of the status of the musculi arrectores pilorum (MAP) in non-primate vertebrates, as compiled from the literature. “Comments” are from original sources, except that MAP has been used as an abbreviation throughout.
Class
|
Order
|
Family
|
Genus and/or species
|
MAP (Present, Absent or Variable)
|
MAP Coding: Present (1) or Absent (0)
|
Description
|
Comments
|
Reference
|
Reptilia
|
Squamata
|
All families
|
|
Present
|
1
|
Used for scales
|
Dermal muscles, which move imbricated scales relative to one another, and subcutaneous muscles, which move the skin relative to underlying body structures, have been documented for snakes and lizards.
|
|
Aves
|
All orders
|
All families
|
|
Present
|
1
|
|
Feather muscles classified into three types of smooth muscle according to function: (a) the arrector muscle, which is attached at one end to the neck of one feather follicle and at the other end to the base of a follicle anterior to it; (b) the depressor muscles, which pass from the neck of one feather follicle to the base of another follicle posterior to it; and (c) repressor muscles, which that pass from the neck of one follicle to the neck of another follicle and draw the feathers together with no depression or erection.
|
|
Mammalia
|
Monotremata
|
Tachyglossidae
|
Tachyglossus
|
Absent
|
0
|
(akin to that of birds)
|
Erects spines by contracting cross striated skin muscles
|
|
Mammalia
|
Diprotodontia
|
Phalangeridae
|
Trichosurus vulpecula
|
Present
|
1
|
|
|
|
Mammalia
|
Pholidota
|
Manidae
|
Manis pentadactyla
|
Absent
|
0
|
|
|
|
Mammalia
|
Lagomorpha
|
Leporidae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Lagomorpha
|
Ochotonidae
|
Ochotona spp.
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Bathyergidae
|
|
Absent
|
0
|
Variable in species
|
While they may function to increase tactile sensitivity and not as erectile organs, it seems somewhat more possible that they may have an erectile function in these specimens because the usual arrector muscle is lacking.
|
|
Mammalia
|
Rodentia
|
Castoridae
|
|
Absent
|
0
|
|
|
|
Mammalia
|
Rodentia
|
Caviidae
|
Hydrochoerus hydrochaeris
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Chinchillidae
|
Chinchilla lanigera
|
Present
|
1
|
Multiple hair associated with each MAP
|
Each group of hairs has a single MAP
|
|
Mammalia
|
Rodentia
|
Cricetidae
|
Myodes gapperi
|
Present
|
1
|
|
Not mentioned except to say they are not enlarged on flank skin, implying they are present.
|
|
Mammalia
|
Rodentia
|
Ctenodactylidae
|
|
Present
|
1
|
|
Only on breast
|
|
Mammalia
|
Rodentia
|
Dipodidae
|
|
Present
|
1
|
Not found in every specimen
|
Usually present often thin
|
|
Mammalia
|
Rodentia
|
Geomyidae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Gliridae
|
Selvenia
|
Present
|
1
|
Thin
|
|
|
Mammalia
|
Rodentia
|
Heteromyidae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Hystricidae
|
Hystrix spp.
|
Present
|
1
|
Powerful
|
|
|
Mammalia
|
Rodentia
|
Muridae
|
|
Present
|
1
|
Thin to well- developed
|
|
|
Mammalia
|
Rodentia
|
Muridae
|
Rattus spp.
|
Present
|
1
|
|
Not well-developed
|
|
Mammalia
|
Rodentia
|
Myocastoridae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Sciuridae
|
|
Present
|
1
|
|
Very many have
|
|
Mammalia
|
Rodentia
|
Sciuridae
|
Marmota
|
Present
|
1
|
|
|
|
Mammalia
|
Rodentia
|
Spalacidae
|
|
Present
|
1
|
|
Not on breast
|
|
Mammalia
|
Macroscelidea
|
Macroscelidae
|
Elephantulus rozeti
|
Absent
|
0
|
|
|
|
Mammalia
|
Primates
|
Strepsirhini
|
|
Variable
|
Mostly 0
|
|
Present on tail only of most species
|
See main text Table 2
|
|
Primates
|
Tarsiidae
|
|
Absent
|
0
|
|
|
See main text Table 2
|
|
Primates
|
Anthropoidea
|
|
Present
|
1
|
|
|
See main text Table 2
|
Mammalia
|
Scandentia
|
Tupaiidae
|
Tupaia glis
|
Present
|
1
|
Slender
|
The follicles have a large bulge to which are attached delicate strands of piliary muscles. However, Sokolov could not find these in his specimen.
|
|
Mammalia
|
Chiroptera
|
Chiroptera (all families)
|
|
Absent
|
0
|
Specialized areas only
|
Only in specialized skin, not on wings
|
|
Mammalia
|
Dermoptera
|
Cynocephalidae
|
Cynocephalus temminckii
|
Absent
|
0
|
|
|
|
Mammalia
|
Insectivora
|
Tenrecidae
|
|
Present
|
1
|
Well- developed
|
Specialized to quills
|
|
Mammalia
|
Insectivora
|
Erinaceidae
|
Erinaceus europaeus
|
Present
|
1
|
|
|
|
Mammalia
|
Insectivora
|
Solenodontidae
|
|
Present
|
1
|
Strong
|
|
|
Mammalia
|
Insectivora
|
Soricidae
|
|
Absent
|
0
|
|
|
|
Mammalia
|
Insectivora
|
Talpidae
|
Desmana moschata
|
Absent
|
0
|
|
|
|
Mammalia
|
Insectivora
|
Talpidae
|
Scapanus townsendii
|
Present on dorsum only
|
1
|
Slender
|
Absent on chest and venter
|
|
Mammalia
|
Carnivora
|
Canidae
|
|
Present
|
1
|
|
Thick
|
|
Mammalia
|
Carnivora
|
Canidae
|
Cuon alpines
|
Present
|
1
|
|
Poorly developed
|
|
Mammalia
|
Carnivora
|
Felidae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Carnivora
|
Mustelidae
|
Mustela putorius furo
|
Present
|
1
|
|
Variable thickness
|
|
Mammalia
|
Carnivora
|
Mustelidae - Lutrinae
|
Lutra lutra
|
Absent
|
0
|
Aquatic
|
For streamlining
|
|
Mammalia
|
Carnivora
|
Otariidae
|
Eumetopias jubatus; Lobodon carcinophagia
|
Absent
|
0
|
|
For streamlining
|
|
Mammalia
|
Carnivora
|
Ursidae
|
|
Vestigial
|
1
|
|
Rare and not on breast of Ursus arctos and thin on U. maritimus
|
|
Mammalia
|
Carnivora
|
Viverridae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Artiodactyla
|
Bovidae
|
|
Present
|
1
|
Well developed in most
|
|
|
Mammalia
|
Artiodactyla
|
Camelidae
|
Camelus dromedarius
|
Present
|
1
|
|
Animals sweat when temperatures reach 44C; sweat is at end of hair.
|
|
Mammalia
|
Artiodactyla
|
Camelidae
|
|
Present in four taxa
|
1
|
Rarely Absent
|
In llamas, well-developed MAP are associated with larger hair follicles in the areas of long dense hair-coat, whereas they are small and rudimentary in areas with short sparse hair-coat and referred to as “thermal windows.”
|
|
Mammalia
|
Artiodactyla
|
Cervidae
|
|
Present
|
1
|
Well developed in most
|
|
|
Mammalia
|
Artiodactyla
|
Giraffidae
|
|
Present
|
1
|
|
|
|
Mammalia
|
Artiodactyla
|
Moschidae
|
Moschus moschiferus
|
Present
|
1
|
|
|
|
Mammalia
|
Artiodactyla
|
Suidae
|
|
Present
|
1
|
|
Only at the bristles and very powerful used as shock absorber
|
|
Mammalia
|
Artiodactyla
|
Tayassuidae
|
|
Present
|
1
|
|
Only at the bristles and very powerful used as shock absorber
|
|
Mammalia
|
Cetacea
|
Cetacea (all families)
|
|
Absent
|
0
|
|
|
|
Mammalia
|
Perissodactyla
|
Equidae
|
Equus spp.
|
Present
|
1
|
|
|
|
Mammalia
|
Perissodactyla
|
Rhinocerotidae
|
Rhinoceros spp.
|
Present
|
1
|
|
|
|
Mammalia
|
Hyracoidea
|
Procaviidae
|
|
Present
|
1
|
Typically thin
|
|
|
Mammalia
|
Sirenia
|
Sirenia (all families)
|
|
Absent
|
0
|
|
Aquatic
|
|
Mammalia
|
Proboscidea
|
Elephantidae
|
|
Absent
|
0
|
|
|
|
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