Megacricetodon minor (Lartet, 1851)

Hír, J., 2013, Early and Middle Miocene (MN 5 - MN 6) transitional rodent fauna from Litke (North Hungary, Nógrád County), Fragmenta Palaeontologica Hungarica 30, pp. 101-137 : 116-120

Megacricetodon minor (Lartet, 1851)

( Figs 23–34)

Material and measurements (mm) –

Locality No. inv. MMP. Position L W Figures Litke 1 2012.52. M1 1.64 0.98 23

Litke 1 2012.53. M1 1.55 0.98

Litke 1 2012.54. M1 1.55 0.98 24

Litke 1 2012.55. M1 1.48 0.91

Litke 1 2012.56. M1 1.48 0.98

Litke 1 2012.57. M1 1.50 0.97

Litke 1 2012.58. M1 1.61 0.97

Litke 1 2012.59. M1 1.50 0.93

Litke 1 2012.60. M1 1.41 0.85

Litke 1 2012.61. M1 1.48 0.92

Litke 1 2012.62. M1 1.57 0.98 25

Litke 1 2012.63. M1 1.39 0.90

Litke 1 2012.64. M1 1.55 0.98

Litke 1 2012.65. M1 1.47 0.98

Litke 1 2012.66. M1 1.47 0.90

Litke 1 2012.67. M1 1.64 0.98

Litke 1 2012.68. M1 1.48 0.94

Litke 1 2012.69. M1 1.50 0.92

Litke 1 2012.70. M1 1.55 1.01

Litke 2 2012.84. M1 1.45 0.92

Litke 2 2012.87. M1 1.45 0.92

Litke 1 2012.71. M2 1.20 0.91

Litke 1 2012.72. M2 1.26 0.99

Litke 1 2012.73. M2 1.11 0.91

Litke 1 2012.74. M2 1.22 0.99

Litke 1 2012.75. M2 1.19 0.92 26

Litke 1 2012.76. M2 1.20 0.98 27

Litke 1 2012.77. M2 1.13 0.98

Litke 1 2012.78. M2 1.22 0.99

Litke 1 2012.79. M2 1.12 0.90

Litke 1 2012.80. M2 1.18 0.97

Litke 1 2012.81. M2 1.12 0.94

Litke 1 2012.82. M2 1.27 1.12

Litke 1 2012.83. M2 1.22 0.98

Litke 2 2013.85. M2 1.09 0.90

Litke 2 2013.98. M2 1.08 0.91

Litke 1 2012.84. M3 5.7 6.0

Litke 1 2012.85. M3 5.4 5.1

Litke 1 2012.86. M3 4.9 5.1

Litke 1 2012.87. M3 5.1 5.2

Litke 1 2012.88. M3 5.6 5.4

Litke 1 2012.89. M3 5.8 5.7

Litke 1 2012.90. M3 5.5 5.7

Litke 1 2012.91. M3 6.0 5.7

Litke 1 2012.92. M3 5.5 6.0 28

Litke 2 2013.85. M3 4.9 5.3 29

Litke 1 2012.93. m1 1.40 0.91 30

Litke 1 2012.94. m1 1.41 0.88

Litke 1 2012.95. m1 1.37 0.90

Litke 1 2012.96. m1 1.40 0.84

Litke 1 2012.97. m1 1.37 0.88

Litke 1 2012.98. m1 1.36 0.84

Litke 1 2012.99. m1 1.39 0.91

Litke 1 2012.100. m1 1.34 0.84

Litke 1 2012.101. m1 1.39 0.87

Litke 1 2012.102. m1 1.41 0.90

Litke 1 2012.103. m1 1.41 0.88

Litke 1 2012.104. m1 1.37 0.85

Litke 1 2012.105. m1 1.43 0.94 31

Litke 1 2012.106. m1 fragm. – –

Litke 1 2012.107. m1 1.30 0.77

Litke 1 2012.108. m1 1.33 0.84

Litke 1 2012.109. m1 1.44 0.94

Litke 1 2012.110. m1 1.40 0.84

Litke 1 2012.111. m1 1.44 0.92 Litke 1 2012.112. m1 fragm. – –

Litke 1 2012.113. m1 1.39 0.91

Litke 1 2012.114. m1 1.41 0.91

Litke 1 2012.115. m1 1.43 0.85 32

Litke 2 2013.88. m1 1.40 0.87

Litke 2 2013.89. m1 1.37 0.83

Litke 2 2013.90. m1 1.34 0.81

Litke 2 2013.92. m1 1.30 0.83

Litke 2 2013.93. m1 1.34 0.81

Litke 1 2012.116. m2 1.08 0.87

Litke 1 2012.117. m2 1.25 0.99 33

Litke 1 2012.118. m2 1.12 0.91

Litke 1 2012.119. m2 1.09 0.84

Litke 1 2012.120. m2 1.12 0.92

Litke 1 2012.121. m2 1.11 0.91

Litke 1 2012.122. m2 1.25 0.95

Litke 1 2012.123. m2 1.13 0.90

Litke 1 2012.124. m2 1.20 0.97

Litke 1 2012.125. m2 1.19 0.92

Litke 1 2012.126. m2 1.12 0.95

Litke 1 2012.127. m2 1.19 0.97

Litke 1 2012.128. m2 1.19 0.92

Litke 1 2012.129. m2 1.16 0.92

Litke 1 2012.130. m2 1.23 1.05

Litke 1 2012.131. m2 1.15 0.90

Litke 1 2012.132. m2 1.12 0.85

Litke 1 2012.133. m2 1.20 0.99

Litke 2 2013.94. m2 1.16 0.87

Litke 2 2013.95. m2 1.08 0.91

Litke 2 2013.96. m2 1.09 0.85

Litke 2 2013.99. m2 1.09 0.85

Litke 1 2012.134. m3 1.02 0.85

Litke 1 2012.135. m3 0.92 0.73

Litke 1 2012.136. m3 0.97 0.78

Litke 1 2012.137. m3 0.98 0.77

Litke 1 2012.138. m3 0.99 0.84 34

Litke 1 2012.139. m3 1.06 0.87

Litke 1 2012.140. m3 0.99 0.77

Litke 2 2013.100. m3 0.87 0.71

Litke 2 2013.101. m3 0.90 0.74

Litke 2 2013.102. m3 – 0.70

Description – M1 – Anterocone is splitted (consists of two cuspulas). Those are separated by a shallow groove in the mesial surface. The groove does not reach the basis of the crown. An anterocingulum is developed in the mesial base (5 out of 21 specimens). In one specimen the lingual anteroloph is continued along the lingual surface of the protocone up to the anterior base of the hypocone. The anterolophule runs to the lingual cuspula of the anterocone (14/21), or ramified (Y-shape) and the two branches are connected to the two cuspulas (7/21). Protolophule 1 (reaching the anterior basis of the paracone) is developed only in one molar. The protolophule 2 is nearly transversally directed and connected to the posterior angle of the protocone. Paracone posterior spur is missing (2/21), or short (does not reach the mesoloph) (4/21), or long (reaches the mesoloph) (8/21). In 5 cases the spur is long, but not connected to the mesoloph, because the mesoloph is short. In one case the spur is “hyperdeveloped”: reaches the anterior surface of the metacone on the labial margin (but not connected to the mesoloph). Mesoloph can be also long, either runs up to the labial margin (1/21), or does not reach the labial margin (7/21), it may be middle sized (6/21), or short (7/21). Entomesoloph is developed in one specimen, but it is not complete: does not reach the centroloph. The metalophule starts from the centre of the hypocone (2/21), from the posterior angle of the hypocone (8/21), or from the posteroloph (10/21). In one case the posterolophule is doubled: one of them starts from the posterior angle of the hypocone, the other one starts from the posterolophule. Three roots.

M2 – Protolophule 1 and 2 are equally developed (7/15), or only the protolophule 1 is observed (8/15). Paracone posterior spur is either missing (2/15), short (2/15), or long and reaches the mesoloph (5/15), or long, but does not reach the mesoloph because it is labially curved (2/15), or “hyperdeveloped”, reaches the anterior basis of the metacone (4/15). Mesoloph reaches the labial margin (3/15), or long, but does not reach the labial margin (11/15), or middle developed (1/15). Metalophule starts above the hypocone (12/15), from the centre of the hypocone (1/15), or from the posterior angle of the hypocone (2/15). Three roots.

M3 – Labial anteroloph arm is constant; there is a trench between the labial anteroloph and the metaloph-metacone. Lingual anteroloph arm is missing or incipient. The protolophulus starts from the anterior angle of the protocone. Lingual sinus is found only in one case. The axioloph is complete (5/9), interrupt- ed (does not reach the protolophulus) (1/9), or missing (3/9). Centrocone is well developed (7/9), or fused into the mesoloph (2/9). A small hypocone is developed, the metacone is incipient (2/9), or fused into the posteroloph (7/9). Three roots.

m1 – Anteroconid centrally positioned and unicuspid (undivided). The anterolophulid is developed in the longitudinal axis of the tooth and either connected centrally to the anteroconid (18/27), or connected to the labial angle of the anteroconid (9/27). The anterolophulid is simple (21/27), or bears a spur (6/27). The lingual anterolophid is complete (20/27), or developed only as a stylid (6/27), or missing (1/27). The mesolophid reaches the lingual margin (1/28), medium sized (9/28), short (11/28), or missing (7/28). A low ectomesolophid is found in one m1. Well-developed labial posterolophulid branch is found only in one case. Two roots.

m2 – The crosspoint of the anterolophulids, protoconid anterior arm and metaconid is developed as a cuspula, “quasi anteroconid” (6/22). Lingual anterolophid is missing (7/22), short (7/22), middle developed (6/22), or long (2/22). Mesolophid is missing (3/23), short (4/23), middle developed (14/23), or long, but does not reach the lingual margin (1/23). Labial posterolophulid arm is developed in one case.

m3 – Lingual anterolophid is missing (3/9), short (1/9), middle developed (4/9), or long (1/9). Mesolophid is missing (9/9).

Comments – On the basis of the metric characters the large and middle-sized Megacricetodon species can be ruled out. Among the small-sized Megacricetodon species M. debruijni and M. minutus are out of consideration because of the significant age difference. These species appeared in the MN7/8 zone and their special morphological feature is the anteriorly curved lingual sinus in M2 medium sized protocone posterior arm. This configuration is missing in Litke.

By classifying of the Megacricetodon population of Litke the real possibilities are M. minor , M. primitivus and M. collongensis . Referring to DAAMS & FREUDENTHAL (1988) M. minor differs from M. primitivus among others characters by the more frequent double protolophule in M2. The frequency of this configuration is between 50–100% in the Central European M. minor populations. In Spanish M. primitivus materials this value is between 9–33%. The double protolophule is found in 47% of M 2 in Litke, which is closer to M. minor . The frequency of the double protolophule in M2 is a good marker for the distinction of M. collongensis and M. minor ( DAAMS & FREUDENTHAL 1988) . In the Spanish M. collongensis populations this value is between 4–32%. According to the above citated authors M. minor differs from M. collongensis by the longer mesolophids in m1 and m2. Here we listed the frequency of the morphotype where the mesolophid is completely missing ( Table 3).