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Table 2 Morphological comparisons among Abrawayaomys and other members of the Sigmodontinae

From: The phylogenetic position of the enigmatic Atlantic forest-endemic spiny mouse Abrawayaomys (Rodentia: Sigmodontinae)

Character Abrawayaomys Rhagomys b Phaenomys d Thomasomys f Aepeomys g Akodon Reithrodon
Plantar pads 6 6 6 6 6 6 4
Hindfoot surface Smooth? Smooth Squamated Smooth Smooth Squamated Squamated
Mammae 6a 6 8 6 6 8 8
Spines Present Presentc Absent Absent Absent Absent Absent
Relation of tail length (LT) to head-body length (HB) LT < = > HB LT ≤ HB LT > > HB LT < = > HB LT > HB LT ≤ HB LT < < HB
Rostrum Short Short Long Long Long, rostral tube developed Moderate Moderate
Interorbit Hourglass-shaped or slightly convergent, with rounded margins Convergent, with beaded margins Hourglass-shapede, with beaded margins Hourglass-shaped, with rounded margins Hourglass-shaped, with rounded margins Hourglass-shaped, with rounded margins Symmetrically constricted, with parallel margins
Palate Typically short Long Short Short Short Short Long
Mesopterygoid fossa Not fenestrated Not fenestrated Not fenestrated Not fenestrated Not fenestrated Fenestrated Fenestrated
Alisphenoid strut Typically present Present Absent Present ? Typically present Present
Tegmen tympani Overlaps squamosal Overlaps squamosal Overlaps squamosal Overlaps squamosal Overlaps squamosal Overlaps squamosal Does not overlap squamosal
Carotid circulation Pattern 1 Pattern 3 Pattern 1 Pattern 1 Pattern 1 Pattern 1 Pattern 3
Capsular process Present Present Absent Absent Absent Typically present Present
Retromolar fossa Enlarged Enlarged Not enlarged Not enlarged Not enlarged Not enlarged Not enlarged
Molar design Intermediate to alternate, crested Opposite, crested Opposite, crested Opposite, crested Opposite, crested Intermediate, crested to terraced Alternate, plane
Anteromedian flexus Patent Patent Patent Patent Patent Patent Not patent
Mesoloph on M1 Present, small Present, large Present, large Present, large Present, large Present, small Absent
M3 reduction to M2 Much reduced Moderately Weakly Moderately Moderately to reduced Much reduced Weakly
Incisors Orthodont to proodont Orthodont Opisthodont Opisthodont Opisthodont Typically opisthodont Opisthodont
Incisive foramina Reaching anterior face M1 Very short Reaching anterior face M1 Reaching anterior face M1 Reaching anterior face M1 Reaching protocone M1 Reaching protocone M1
Subsquamosal foramen Present Present Absent Present Present Present Present
Number of ribs 12 13 12 13 13 13 12
Gall bladder Absent Absent Present Present Present Typically presenth Present
  1. aInguinal, abdominal, and postaxial pairs (Pardiñas, unpublished data). bBased on Rhagomys longilingua, after Luna and Patterson (2003). c Rhagomys rufescens lacks spines (cf. Luna and Patterson 2003). dData from Voss et al. (2002) and Pardiñas (unpublished data). eScored as ‘convergent’ by Pacheco (2003, p. 43). fVariation in this genus is remarkable (cf. Pacheco 2003); herein, we follow Voss (1993). gBased on Aepeomys lugens, after Voss et al. (2002). h Akodon montensis lacks gall bladder (cf. Geise et al. 2004).