Home

Article Search

 

List of endocranial character states from Nesophontes (several characters were adopted and modified from Macrini et al., 2007a).

Character 1

Olfactory bulb cast percent composition: 6% or greater = 0; less than 6% =1

Nesophontes olfactory lobe percent composition from total brain volume ranges from 20-25% (score of = 0). Nesophontes approaches the overall percent composition of Tenrec and Hemicentetes the most (Stephan and Andy, 1982). That of Solenodon is 17.95%, and from other insectivorans reported by Stephan and Andy (1982).

Character 2

Width to length ratio of olfactory lobes: longer than wide (aspect ratio < 0.9) = 0; wider than long (aspect ratio > 1.1) = 1; equivalent (aspect ratio between 0.9 and 1.1) = 2. Nesophontes sp. scores = 2.

Character 3

Accessory olfactory bulb casts: absent=0; present=1.

Accessory olfactory bulbs are not always present in the endocranial casts of extinct or extant mammals (Bauchot and Stephan, 1967; Macrini et al., 2007a). Stephan and Andy (1982) reported “no accessory bulbs” on the olfactory lobes of Solenodon paradoxus. This state is scored = 0 here, was considered unique in Solenodon in comparison to other insectivoran-grade mammals such as Erinaceus, Sorex, Tenrec, Hemicentetes, and Microgale. It also scores = 0 in Nesophontes .

Such accessory bulbs apparently receive nerve fibers (or projections) from the vomero-nasal organ and are involved in the detection of pheromones (Nieuwenhuys et al., 1998; Macrini et al., 2007a).

Character 4

Olfactory bulb tracts (or peduncles): not visible on endocasts = 0; visible on endocasts = 1. Nesophontes sp. scores = 1.

Character 5

Circular fissure: Absent or shallow on endocast = 0; marked or deep on endocast = 1. Nesophontes sp. scores = 1.

Character 6

Surface of cerebral hemisphere endocasts: lissencephalic or smooth = 0; gyrencephalic or convoluted = 1. Nesophontes sp. scores = 0.

Character 7

Rhinal fissure seen on endocast: not visible or absent = 0; visible or present on endocast = 1. Nesophontes sp. scores = 1.

Character 8

Lateral extent of the cerebral hemisphere cast: medial to or even with the parafloccular casts = 0; clearly extending laterally beyond the parafloccular casts = 1. Nesophontes sp. scores = 1.

Character 9

Cast of the superior sagittal sinus: not visible on dorsal surface of the endocast = 0; visible =1.

Nesophontes sp. scores = 1. Note: this character is often not visible on endocasts if located deep or thickly covered by the meninges (Macrini et al., 2007a).

Character 10

Ossified falx cerebri: absent = 0; present = 1. Nesophontes sp. scores = 0.

Character 11

Ossified tentorium: absent = 0; present posteromedially = 1; present laterally = 2; completely present = 3. These stages are explained in Macrini et al. (2007a). Nesophontes sp. scores = 0.

Character 12

Wide gap between the neocortex and cerebellum casts: absent = 0; present = 1. Nesophontes sp. scores =? But probably = 1.

This character is problematic in Nesophontes because there are slight discrepancies between the natural and digital endocasts. Natural endocasts show a slight indentation or gap between the neocortex and cerebellum that seems very shallow in the digital endocast. However, imprints within this region of the osseous braincase support a shallow gap between these structures.

Character 13

Extent of the tectum and colliculi casts: below = 0; at the same level of the vermis = 1; above = 2. Nesophontes sp. scores = 1.

Character 14

Extent of vermis cerebelli: cast of vermis extending to or even with the parafloccular casts = 0; vermis remains behind the parafloccular casts = 1; vermis extends beyond parafloccular casts = 2. Nesophontes sp. scores = 2.

Character 15

Extent of cerebellar hemisphere casts not visible on endocasts = 0; visible = 1. Nesophontes sp. scores = 1.

Character 16

Shape of parafloccular casts: cone-shaped = 0; broad and round = 1; ovoid, large, and oriented posterolaterally = 2; long and cylindrical = 3. Nesophontes sp. scores = 2.

Character 17

Prootic canal visible on squamosal bone of the skull (character taken from Wible, 2008): absent = 0; present = 1. Both Cuban Nesophontes score = 1. The orbitotemporal grove may be associated with this structure in Nesophontes , as it is in Solenodon (ecps: Wible, 2008: figure 21, p. 349).

Prootic canals are not known from any other placental mammal. They are reported from Mesozoic mammaliaforms and several Cenozoic eutherians, monotremes, and some marsupials. See Wible (2008) for discussion of this character and literature.

Character 18

Canal for carotid arteries relative to the hypophysis: posterolaterally positioned = 0; anterolaterally positioned = 1. Nesophontes sp. scores = 0.

Character 19

Orbitotemporal groove not visible over perotic portion of squamosal cast = 0; visible on endocast = 1. Nesophontes sp. scores = 1. This groove can represent the cast of a meningeal vessel.

Character 20

Nasoturbinal foramina located inferior to ectoturbinal foramina II not on a depression = 0; on depression = 1. Nesophontes sp. scores = 1.

 

logo smallPalaeontologia Electronica
Webmaster
1998–2019
22 years of electronic palaeontology

PE is archived by CLOCKSS and LOCKSS programs.