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FIGURE 1. Natural (1), digital (2), and radiographic images (3) of Nesophontes spp. crania used in this study. 1, these skulls were the source of natural endocasts for Nesophontes micrus (C145) and Nesophontes major (C181) shown in Figures 1 and 2. 2, Digital rendering of N. major skull (C133) from which the digital endocast in Figure 5 was reconstructed. 3, are negative and positive lateral radiographs of Nesophontes spp. endocranial morphology and space.

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FIGURE 2. Natural endocranial casts of Cuban Nesophontes spp. 1, superior, and right lateral view of Nesophontes major (specimen number C181) endocasts. 2-3, superior and right lateral views of Nesophontes micrus endocasts. 2, Nesophontes micrus (C145); 3-4, are not cataloged.

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FIGURE 3. Anatomical terminology of Nesophontes endocranial casts. 1, superior and lateral views of Nesophontes major endocranial cast (C181). 2, superior and lateral views of Nesophontes micrus (C145) specimen. 3, single view of partial endocranial cast extracted from an uncataloged N. micrus skull. Abbreviations of anatomical terminology: Cb cerebellum; cs superior colliculi; fan annular or circular fissure; Iar internal auditory region; lal lateral lobe of cerebellum; las lateral transverse sinus; Ncx neocortex; Ob olfactory lobes; otg orbitotemporal groove; Ocx olfactory (=piriform) cortex; Pfl paraflocculus; rhf rhinal fissure; sas sagittal sinus or longitudinal sinus; Sphr sphenorbital region; Sv confluence of the transverse and sagittal sinuses; Vc cerebellar vermis. A and P stand for anterior and posterior.

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FIGURE 4. Natural endocranial casts extracted from Nesophontes spp. skulls. (4.1) Nesophontes major hindbrain fragment; (4.2) N. major olfactory lobes; (4.3-4.4) Nesophontes micrus superior (4.3) and left lateral (4.5) views of a partial hindbrain. Cb cerebellum; cs superior colliculi; lal lateral lobe of cerebellum; Ob olfactory lobes; op olfactory peduncle; Pfl paraflocculus; Ts transverse sinus canal; Ts-c confluence of the transverse and sagittal sinuses. A and P stand for anterior and posterior.

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FIGURE 5. Digital endocranial cast of Nesophontes major (C133) in right lateral (1), anterior (2), and inferior (3) views. Abbreviations: Cb cerebellum; cc possible cast of spinal cord space; cs superior colliculi; fan annular or circular fissure; hy hypophyseal fossa; Iar internal auditory region; lal lateral lobe of cerebellum; las lateral transverse sinus; Ncx neocortex; Ob olfactory lobes; Och. optic chiasm; Ocx olfactory (=piriform) cortex; ot olfactory nerve fibers; otg orbitotemporal groove; Pfl paraflocculus; rhf rhinal fissure; sas sagittal sinus or longitudinal sinus; Sphr sphenorbital region; Sv confluence of the transverse and sagittal sinuses; Vc cerebellar vermis. A and P stand for anterior and posterior.

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FIGURE 6. Volume rendering of Nesophontes major (C133) endocranial space in lateral (1) and oblique (2) views showing possible olfactory nerve fibers (onf), sylvian fissure (S. f.), and rhinal fissure (rhf). A and P stand for anterior and posterior.

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FIGURE 7. Endocranial casts of Cuban Nesophontes spp . Nesophontes micrus (C437) first column. Endocast volume: 0.580 mL, encephalization quotients (EQ 2 and 3): 0.21 and 0.33. Nesophontes micrus (C436), second column. Endocast volume: 1.231 mL, EQ 2 and 3: 0.33 and 0.52. Nesophontes major (270), third column. Endocast volume: 0.729 mL, EQs: 0.27 and 0.43. Nesophontes major (C133), fourth and last column. Endocast volume: 0.888 mL, EQs: 0.36 and 0.57.

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FIGURE 8. Cribriform and olfactory regions in Nesophontes major (1) and Nesophontes micrus (2). Abbreviations: ar annular ridge; As alisphenoid; cef cribroethmoidal foramen; cg crista galli; ec ectoturbinal foramina; etI ethmoturbinal foramina; fo foramen ovalae; hs horizontal sulcus; Js jugun sphenoidalis; nc nasocribriform foramina; ntf nasoturbinal foramina; of optic foramen for optic nerve; off olfactory fossa; otc orbitotemporal canal; psp parasphenoid plate; sof sphenorbital fossa; sor sphenorbital ridge. A and P stand for anterior and posterior.

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FIGURE 9. Endocranial morphology of Nesophontes micrus and Nesophontes major calotte showing slight differences in tectum and transverse sinus. Top arrows point to the confluence of the transverse sinus and the colliculi fossae. A and P stand for anterior and posterior.

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FIGURE 10. Idealized brain reconstruction of Nesophontes spp (1), and Solenodon paradoxus (2) in superior and lateral views. The brain of Nesophontes is a composite reconstruction based on natural and digital casts. Solenodon paradoxus was drawn from photographs of Stephen and Andy (1982:541, figures 20-22). Lines and labels on the lateral views indicate similar morphologic features. Olfactory lobes are in red, neocortex is in blue, and posterior brain (part of midbrain and cerebellum) is in green. Specimens are not to same scale. Abbreviations: Cb cerebellum; cs superior colliculi; Fan annular or circular fissure; Iar internal auditory region; lal lateral lobe of cerebellum; las lateral transverse sinus; Ncx neocortex; Ob olfactory lobes; Och optic chiasm; Ocx olfactory (=piriform) cortex; onf olfactory nerve fiber; otg orbitotemporal groove; Pfl paraflocculus; Pof post-orbital fissure; rhf rhinal fissure; sas sagittal sinus or longitudinal sinus; Sphr sphenorbital region; Sv confluence of the transverse and sagittal sinuses; T tectum; Vc cerebellar vermis. A and P stand for anterior and posterior.

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FIGURE 11. Brain morphology of selected extinct and extant mammals, including Nesophontes spp. Upper row contains extant placentals and marsupials. Lower row contains extinct taxa and Nesophontes . Olfactory lobes are in red, neocortex is in blue, and hindbrain is in green. Scale bar equals 10 mm. Sources: Monodelphis domestica drawn from Rowe et al. (2011); Solenodon paradoxus from Allen (1910); Tenrec ecuadatus from Stephan and Andy (1982); Eoryctes melanus from Thewissen and Gingerich (1989); Hyopsodus lepidus from Orliac et al. (2012); Vincelestes neuquenianus from Macrini et al. (2007a) Nesophontes taxa reported here, and the remaining from the Comparative Brain Collection at www.brainmuseum.org. A and P stand for anterior and posterior. Scale bar = 1 cm.

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FIGURE 12. Idealized brain reconstruction of Nesophontes major compared to other insectivoran-mammals, plus the Norway rat Rattus norvegicus . Sorex , Blarina , Condylura , Scalopus , and Rattus specimens were redrawn and modified from specimens in the Comparative Brain Collection at www.brainmuseum.org and Sarko et al. (2009). Erinaceous , Tenrec , and Solenodon were drawn from Stephen and Andy (1982). A and P stand for anterior and posterior. Scale bar = 1 cm.

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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.

 

 

TABLE 1. Linear and volumetric mean values of Nesophontes natural and digital endocasts.

¹ Total cranium length range (minimum and maximum) taken from N. major (n = 24) and N. micrus (n = 12) from the same assemblage. * Estimated body mass calculated from the relationship y = 3.68x - 3.83, where y = log10 (body mass in grams), and x = log10 (skull length in mm) following Luo et al. (2001) and Rowe et al . (2011); EQ² formula from Jerison (1973), and EQ³ formula from Eisenberg (1981). Greater than (>) and less than (<) signs used are to indicate measurements on incomplete specimens. The number given after the sign is the minimum measurement that was taken on the specimen. The labels L (=left) and R (=right) are applied to the measurements of bilateral structures such as the olfactory lobes.

Measurement

N. micrus (C145)

N. major (C181)

N. major (C133)

N. micrus (C436)

 

Natural Endocasts Digital Endocasts

Cranium length (mm) from specimen

> 27.5

> 31.0

32.1

28

Cranium length min. (mm)¹

26.9

30.3

30.3

26.9

Cranium length max. (mm)¹

29.1

32.5

32.5

29.1

Estimated body mass (g)*

97.37

110.2

114.3

99.21

Estimated body length (mm)

≈ 110-135

≈ 120-140

≈120-140

≈ 110-135

y=Log10 value* (Body mass units)

1.99

2.04

2.05

2

x=Log10 value* (Cranial length)

1.44

1.49

1.51

1.45

Estimated endocast volume (ml)

> 0.76

1.09

0.888

1.231

Calculated endocast volume (ml) (from formula)

0.844

0.997

1.043

0.856

Endocast total length (mm)

> 14.48

> 15.18

15.2

14

Endocast total width (mm)

9.86

9.65

9.4

9.7

Olfactory bulb length (mm)

3.65 - 3.69

R 3.60

L 3.0 - R 3.1

incomplete

Olfactory bulb width (mm)

7 (both)

R 3.86

6.4 (both)

incomplete

Cerebellum length (mm)

5.97

4.58 - 5.22

6.2

5.9

Cerebellum width (mm)

7.45 - 8.4

7.32

7.7

7.4

Brain-Cranium length ratio

52.6

49

47.3

50

Encephalization Quotient (EQ)²

0.33

0.35

0.36

0.33

Encephalization Quotient (EQ)³

0.52

0.56

0.57

0.52

 

orjoJohanset Orihuela
Department of Earth and Environment (Geosciences)
Florida International University
Miami, Florida 33199
USA
This email address is being protected from spambots. You need JavaScript enabled to view it.

Johanset Orihuela ARRT RT (R and CT) was born in Matanzas City, Cuba. He holds an Associates degree in Science (in Radiographic Techonology and Computed Tomography) from Professional Trainning Center and Associates in Arts from Miami Dade College (Anthropology). He is currently an undergraduate Paleobiology student at the Florida International University, Miami, Florida, USA. He is interested in Caribbean vertebrate paleontology, with special attention to evolution and extinction of bats and insectivorans.

 
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Endocranial morphology of the extinct Antillean shrew Nesophontes (Lipotyphla: Nesophontidae) from natural and digital endocasts of Cuban taxa

Johanset Orihuela

Plain Language Abstract

Two groups of ancient shrews exist in the fossil record of the Caribbean islands: the Nesophontes and Solenodons. In this paper, I describe for the first time the brain anatomy of Nesophontes from Cuba, through the study of radiographic and natural brain endocasts. Moreover, I compare them to other extinct and living shrews including Solenodon, African tenrecs and other mammals. This study shows that the brain of Nesophontes resembles that of Solenodon and tenrec-like shrews more so than other group of shrews. This similarity suggests that Nesophontes was in life probably nocturnal, with specialized behavior to dig holes and to live underground, with special sensitivity to audition and smell.

Resumen en Español

Morfología endocraneal de la extinta musaraña antillana Nesophontes (Lipotyphla: Nesophontidae) a partir de moldes internos naturales y digitales de taxones cubanos

En el presente estudio se describe la morfología endocraneal del género extinto de musarañas antillanas Nesophontes, a partir de moldes endocraneales tanto naturales como digitales obtenidos de especies cubanas. Los moldes endocraneales muestran lóbulos olfativos desarrollados carentes de bulbos accesorios, un téctum expuesto con colículos superiores visibles, un gran cerebelo y vermis, y un neocórtex liso. La masa corporal se estimó, a partir del tamaño del cráneo, entre 97 y 114 g, proporcionando coeficientes de cefalización entre 0,33 y 0,57. Los moldes endocraneales de Nesophontes son similares morfológicamente a los de Solenodon (la única musaraña caribeña existente), más que a los de otros Lipotyphla como Sorex, Blarina, Erinaceus, o el Afroinsectivora Tenrec. La similitud morfológica con Solenodon, no solo en las estructuras endocraneal sino también en el resto del esqueleto, sugiere una analogía de comportamiento entre los dos géneros. Los marcados colículos superiores, los prominentes lóbulos olfativos, y la anatomía músculo-esquelética facial sugieren que lo más probable es que Nesophontes fuera nocturno y fosorial, apoyándose en la audición, el olfato y el tacto durante su alimentación. Futuros análisis del esqueleto apendicular podrían ayudar a determinar si este género era exclusivamente terrestre o si también explotaba hábitats arbóreos. La suma de los datos de todas estas estructuras morfológicas podría permitir comprender y reconstruir el comportamiento y la ecología de Nesophontes, y la variación morfológica que se observa en el género.

Palabras clave: Cerebro; Moldes internos; Fósiles; Cubano; Nesophontes; Antillano; Extinto; Musaraña

Traducción: Enrique Peñalver

Résumé en Français

Morphologie endocrânienne de la musaraigne Antillaise éteinte Nesophontes (Lipotyphla : Nesophontidae) à partir de moulages naturels et numériques de taxons cubains

Ce papier décrit la morphologie endocrânienne du genre éteint de musaraigne Antillaises Nesophontes, basé sur des moules endocrâniens naturels et numériques extrait d'espèces cubaines. Les moules endocrâniens montrent des lobes olfactifs développés sans bulbes accessoires, un tectum exposé avec un colliculus supérieur visible, un grand cervelet et vermis, et un néocortex lisse. La masse corporelle a été estimée, à partir de la taille du crâne, entre 97 et 114 g, ce qui donne des quotients d'encéphalisation entre 0,33 et 0,57. Les moules endocrâniens de Nesophontes sont morphologiquement semblables à ceux de Solenodon (la seule musaraigne Caraïbes existante), plus qu'aux autres lipotyphliens tels que Sorex, Blarina, Erinaceus, ou l' Afro-insectivore Tenrec. La similarité morphologique avec Solenodon, non seulement dans les structures endocrâniennes mais aussi dans le reste du squelette suggère une analogie de comportement entre les deux genres. Les colliculus supérieurs marqués, les lobes olfactifs importants, et l'anatomie musculo-squelettiques du visage suggèrent que Nesophontes était probablement nocturne et fouisseur, en s'appuyant sur ouïe, l'odorat, et la tactilité de fourrage. De future analyse du squelette appendiculaire peut aider à déterminer si ce genre était uniquement terrestre ou s'il a également exploité des habitats arboricoles. La somme de toutes ces morphologies peut aider à reconstruire et à comprendre le comportement de Nesophontes, l'écologie et la variation morphologique qui est observé dans ce genre.

Mots-clés: cerveau; endocrânes; fossiles; Cubain; Nesophontes; Antilles; éteint; musaraigne

Translator: Kenny J. Travouillon

Deutsche Zusammenfassung

Endocraniale Morphologie der ausgestorbenen Spitzmaus Nesophontes von den Antillen (Lipotyphla: Nesophontidae) mit natürlichen und digitalen endocranialen Ausgüssen kubanischer Taxa

Diese Arbeit beschreibt die endocraniale Morphologie der ausgestorbenen Spitzmaus-Gattung Nesophontes von den Antillen, anhand von natürlichen und digitalen endocranialen Ausgüssen, entnommen von kubanischen Arten. Die endocranialen Ausgüsse zeigen entwickelte olfaktorische Lappen ohne zusätzliche Kolben, ein freigelegtes Tectum mit sichtbaren superioren Colliculi, ein großes Cerebellum und Vermis und einen glatten Neocortex. Ausgehend von der Schädelgröße wurde die Körpermasse auf 97 bis 114 Gramm geschätzt, was einen Encephalisierungsquotienten zwischen 0.33 und 0.57 ergibt. Endocraniale Ausgüsse von Nesophontes sind denen von Solenodon (die einzige heute noch lebende karibische Spitzmaus) morphologisch ähnlich und zwar mehr als anderen Lipotyphla wie Sorex, Blarina, Erinaceus oder der afroinsectivore Tenrec. Die morphologische Ähnlichkeit mit Solenodon, die nicht nur in Bezug auf endocraniale Strukturen besteht, sondern auch im Rest des Skeletts, legt eine Verhaltensähnlichkeit zwischen den beiden Gattungen nahe. Die deutlichen superioren Colliculi, die prominenten olfaktorische Lappen und die muskuloskeletale Gesichtsanatomie deuten darauf hin, dass Nesophontes höchstwahrscheinlich nachtaktiv und grabend lebte und bei der Nahrungssuche auf Hör-Geruchs-und Tastsinn angewiesen war. Weitere Analysen über das appendikuläre Skelett können helfen zu klären, ob diese Gattung ausschließlich terrestrisch lebte oder ob sie auch arboreale Habitate nutzte. Die Summe all dieser Morphologien kann helfen das Verhalten, die Ökologie und die innerhalb der Gattung beobachtete morphologische Variation von Nesophontes zu rekonstruieren und zu verstehen.

Schlüsselwörter: Gehirn; Ausgüsse; Fossilien; kubanisch; Nesophontes; von den Antillen; ausgestorben; Spitzmaus

Translator: Eva Gebauer

Arabic

369 arab

Translator: Ashraf M.T. Elewa