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The use of the species concept in paleontology. Comment on "Nesiotites rafelinensis sp. nov., the earliest shrew (Mammalia, Soricidae) from the Balearic Islands, Spain" by Rofes et al., 2012

Marc Furió and Guillem Pons-Monjo

Plain Language Abstract

Identifying a fossil species is not always an easy task. Individuals included in the same biological species are, by definition, different. Sometimes the boundaries between what is considered a peculiarity of an individual, of a species or of a genus can be somewhat arbitrary. In this work, we provide some examples of morphological variability within rather large fossil populations of shrew from the Balearic Islands (Spain) where only one species per site is present. The oldest record of a shrew in Mallorca hitherto was recently described as a new species based on just a single specimen. After our study, the most reasonable conclusion is that this fragment of mandible is probably not a new species to science but it actually belongs to a previously known species, Nesiotites ponsi.

Resumen en Español

El uso del concepto de especie en paleontología. Comentario sobre "Nesiotites rafelinensis sp. nov., la musaraña (Mammalia, Soricidae) más antigua de las Islas Baleares, España" por Rofes et al., 2012

El representante más antiguo de Nesiotites de Caló d'en Rafelino (Mallorca) ha sido descrito recientemente como una nueva especie (Nesiotites rafelinensis) sobre la base de una sola hemimandíbula con p4-m3. Una revisión en detalle de las extensas colecciones de diferentes especies de Nesiotites de las Islas Baleares pone de manifiesto la existencia de una amplia variación morfológica en estas musarañas del Plio-Pleistoceno. Seis de los siete caracteres diagnósticos de N. rafelinensis caen dentro del rango de variabilidad de N. ponsi, la especie más antigua previamente conocida. Concluimos, por tanto, que no existen caracteres que justifiquen suficientemente la definición de una nueva especie y que, en nuestra opinión, este material debería ser atribuido a N. ponsi o a alguna forma estrechamente relacionada (N. aff. ponsi / N. cf. ponsi).

Palabras clave: Lipotyphla; Nectogalini; Asoriculus; Mallorca; Nesiotites ponsi; variabilidad biológica

Traducción: Miguel Company

Résumé en Français

L'utilisation du concept d'espèce en paléontologie. Commentaire sur "Nesiotites rafelinensis sp. nov., the earliest shrew (Mammalia, Soricidae) from the Balearic Islands, Spain" par Rofes et al., 2012

Le plus ancien représentant de Nesiotites de Caló d'en Rafelino (Majorque) a été récemment décrit comme une nouvelle espèce (Nesiotites rafelinensis) sur la base d'une seule hémimandibule avec p4-m3. Une inspection minutieuse de grandes collections d'espèces différentes de Nesiotites provenant des îles de Baléares révèle une large variation morphologique intraspécifique chez les musaraignes plio-pléistocènes. Six des sept caractères diagnostiques de N. rafelinensis tombent dans la variabilité de l'espèce précédemment connue comme la plus ancienne, N. ponsi. Nous en concluons qu'aucun trait ne supporte suffisamment la définition d'une nouvelle espèce, et de notre point de vue ce matériel devrait être référé à N. ponsi ou à une forme proche (N. aff. ponsi / N. cf. ponsi).

Mots clés: Lipotyphla; Nectogalini; Asoriculus; Majorque; Nesiotites ponsi; variabilité biologique.

Translator: Olivier Maridet

Deutsche Zusammenfassung

Das Artenkonzept in der Paläontologie: Bemerkung zu "Nesiotites rafelinensis sp. nov., die früheste Spitzmaus (Mammalia, Soricidae) der Balearen, Spanien

Schlüsselwörter: Lipotyphla; Nectogalini; Asoriculus; Mallorca; Nesiotites ponsi; biologische Variabilität

Translator: Eva Gebauer

Arabic

336 arab

Translator: Ashraf M.T. Elewa

 

 

TABLE 1. Compared values of lower dental measures in PO, BB and CC. Shadowed files correspond to measurements taken when sample was limited to 25 elements (Pons-Monjo et al., 2012), independently whether left or right, 'in situ' (i.e., in mandible) or not (i.e., loose). White files correspond to the new measurements taken on all measurable left hemimandibles with molar elements 'in situ' from each locality considered. Abbreviations: Ma: mandible; L: length; Lm1-m3: length of the lower molar row; Max: maximum; Min: minimum; N: number of specimens; Par: parameter; SD: standard deviation; TAW: talonid width; TRW: trigonid width; W: width.

 
       

PO

       

BB

       

CC

   
 

Par.

Min.

Mean

Max.

SD

N

Min.

Mean

Max.

SD

N

Min.

Mean

Max.

SD

N

m1 

 

 


 

 

 

L

1.85

2.00

2.20

0.08

25

1.93

2.04

2.19

0.07

25

2.09

2.17

2.31

0.06

25

L

1.83

1.95

2.19

0.06

93

1.94

2.02

2.06

0.05

7

2.05

2.15

2.33

0.07

65

TAW

1.04

1.27

1.40

0.08

25

1.16

1.30

1.38

0.05

25

1.37

1.43

1.55

0.04

25

TAW

1.14

1.29

1.42

0.05

93

1.24

1.35

1.44

0.06

7

1.37

1.49

1.62

0.06

65

TRW

1.02

1.15

1.29

0.08

25

1.03

1.14

1.22

0.06

25

1.13

1.23

1.35

0.05

25

TRW

1.03

1.17

1.31

0.05

93

1.07

1.17

1.22

0.06

7

1.15

1.29

1.47

0.06

65

m2 

 

 


 

 

 

L

1.72

1.84

1.96

0.07

25

1.75

1.87

1.95

0.06

25

1.88

1.99

2.10

0.07

25

L

1.53

1.75

1.94

0.07

93

1.77

1.83

1.92

0.07

5

1.83

1.95

2.18

0.07

65

TAW

1.03

1.12

1.18

0.04

25

1.02

1.12

1.25

0.06

25

1.09

1.21

1.26

0.04

25

TAW

0.99

1.14

1.29

0.06

93

1.08

1.18

1.30

0.08

5

1.13

1.28

1.48

0.07

65

TRW

1.01

1.09

1.15

0.05

25

1.00

1.09

1.23

0.06

25

1.12

1.21

1.29

0.04

25

TRW

0.97

1.13

1.32

0.06

93

1.05

1.15

1.20

0.06

5

1.16

1.29

1.44

0.07

65

m3 

 


 

 

L

1.28

1.36

1.45

0.06

25

1.35

1.44

1.55

0.05

21

1.38

1.50

1.73

0.08

25

L

1.16

1.32

1.45

0.05

93

1.34

1.39

1.51

0.06

7

1.31

1.44

1.58

0.06

65

W

0.73

0.83

0.94

0.05

25

0.72

0.81

0.90

0.05

21

0.77

0.86

0.98

0.05

25

W

0.76

0.89

1.02

0.05

93

0.72

0.84

0.95

0.08

7

0.86

1.01

1.19

0.07

65

Ma 

 

Lm1-3

4.76

4.96

5.09

0.08

25

4.95

5.08

5.28

0.11

7

5.00

5.43

5.64

0.12

25

Lm1-3

4.42

4.88

5.15

0.13

93

4.95

5.08

5.28

0.11

7

5.00

5.32

5.70

0.12

65

 

FIGURE 1. Boxplot comparing the measurements of Nesiotites from Caló d'en Rafelino with the other known fossil populations of the genus in the Balearic Islands. Notice that the only specimen of "N. rafelinensis" falls always within the variability range of N. ponsi from Cap Farrutx and/or N. aff. ponsi from Pedrera de s'Onix. Small circles represent outliers for each population (i.e., values exceeding between 1.5 and 3 times the box height above the top of the box or below its bottom). In the samples from Cap Farrutx with n=2, the box does not represent quartiles, but a total range according to maximum and minimum values provided by Reumer (1979).

figure 1

  FIGURE 2. Left hemimandibles of Nesiotites aff. ponsi from PO (1-4) and N. hidalgo from CC (5-7) showing morphological variability by combination of different states on the considered diagnostic characters of N. rafelinensis. 1-IPS51548; 2-IPS52318; 3-IPS52125 (A-Lingual view; B- Occlusal view); 4-IPS51469; 5-50483 (A- Occlusal view; B- Labial view); 6-IPS50626 (A-Labial view; B-Lingual view); 7-IPS50482. Arrows indicate the distance from the posterior extreme of the mental foramen to the vertical line crossing the tip of the protoconid. Notice that in 3A and 5B (examples randomly selected), any of these possible ways of measuring Hm2 by the lingual or the labial side indicate a more robust mandibular body than that of the specimen from Caló d'en Rafelino. Occlusal (3B, 5A) and lingual views (3A, 6B) of N. aff. ponsi and N. hidalgo have been included to be compared with the holotype of "N. rafelinensis" (Rofes et al., 2012, figure 3). Notice that morphological differences between "N. rafelinensis" and N. aff. ponsi are minimal.

figure 2

 

 

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furioInstitut Català de Paleontologia M. Crusafont
Edifici ICP
Universitat Autònoma de Barcelona
Cerdanyola del Vallès
08193, Barcelona
Spain

Marc Furió graduated in Geology and completed his PhD in Palaeontology at Universitat Autònoma de Barcelona. He is researcher at the Catalan Institute of Palaeontology since 2007. His main topic are the palaeobiology, biostratigraphy and taxonomy of Neogene and Quaternary insectivores, to which he has dedicated all his scientific life. Apart from this strict field of research, he organizes and participates in several activities addressed to all kind of audiences to popularize palaeontology.

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monjoInstitut Català de Paleontologia M. Crusafont
Edifici ICP
Universitat Autònoma de Barcelona
Cerdanyola del Vallès
08193, Barcelona
Spain

Guillem Pons-Monjo graduated in Biology by Universitat de Barcelona, and he got his MSc in Palaeontology in 2010. His master's thesis was supervised by M. Furió and it was focussed on the variability of Nesiotites, an endemic genus of shrews from Mallorca and Menorca (Balearic Islands). He is technical staff of the Catalan Institute of Palaeontology since 2011.