气候变化与早期兔形类的演化：基于内蒙古Ordolagus新材料的研究

doi:10.19615/j.cnki.1000-3118.210325

摘要/Abstract

摘要：

早渐新世是新生代全球气候变化的关键时期。这一时期发生了重大的哺乳动物群转换事件,在欧洲称之为 “大间断”, 在亚洲则为 “蒙古重建”。然而,关于渐新世哺乳动物各谱系的形态变化尚缺少详细探讨。兔形目是现代哺乳动物中多样性最低的类群之一,在全球的化石记录中很常见,尤其是在亚洲。渐新世时,许多古老的始新世兔形类灭绝并被更进步的类群所取代。内蒙古的新发现及对老标本的再研究使我们得以修订鄂尔多斯兔(Ordolagus) (亚洲常见的兔形类,可能源自中-晚始新世的戈壁兔Gobiolagus)。在内蒙古,我们识别出Ordolagus在早渐新世初期就已存在。与亚洲和北美的同期或稍早的兔形类的对比表明,Ordolagus具有一些显著的牙齿形态特征(p3下前边尖发达,颊齿完全高冠,p4-m2下三角座和下跟座舌侧相连等), 这些也是现生兔形类的主要特征。Ordolagus中这些特征的出现与重大全球或区域气候变化同步。对亚洲早期兔形类的进一步研究,并参考其他小哺乳动物与区域气候因素的研究,将有助于完善兔形类作为古气候代用指标的作用。

关键词: 内蒙古, 古近纪, 兔科, 分类学, 演化趋势, 趋同模式, 干旱化/气候恶化

Abstract:

The Early Oligocene is a critical time for global climate changes in the Cenozoic. This epoch witnessed severe mammalian faunal turnovers known as “Grande Coupure” in Europe and “Mongolian Remodelling” in Asia. However, insights about morphological changes in Oligocene mammal lineages have not been explored in detail. One of the least diversified groups of recent mammals, lagomorpha, is globally common in the fossil records, especially in Asia. During the Oligocene, many Eocene archaic lagomorph taxa died out and were replaced by more advanced forms. New findings from Nei Mongol and re-examination of the specimens from older collections enabled a revision of a common Asian lagomorph genus, Ordolagus, which possibly has a close affinity with the Middle-Late Eocene genus Gobiolagus. In Nei Mongol, we recognized the presence of Ordolagus during the basal Early Oligocene. Comparisons with coeval and slightly older lagomorph taxa from Asia and North America show that Ordolagus attained some salient tooth morphological characters (i.e., development of anteroconid on p3, full hypselodonty of cheek teeth, and lingual connection of trigonid and talonid on p4-m2), which are also the key features of modern leporids. The appearance of those morphologic features in Ordolagus is coeval to major global or regional climatic changes. Further investigations on Asian early lagomorphs compared with the study of other small mammals and local climatic factors will be essential to refine the role of lagomorphs as palaeoclimatic proxies.

Key words: Nei Mongol, northern China, Paleogene, Leporidae, taxonomy, evolutionary trends, convergence patterns, aridity/climate deterioration

中图分类号:

Q915.873

安晓青, 张兆群. 气候变化与早期兔形类的演化：基于内蒙古Ordolagus新材料的研究. 古脊椎动物学报, 2021, 59(2): 138-168.

Chiara ANGELONE, ZHANG Zhao-Qun. Climate change and evolution of early lagomorphs (Mammalia): a study perspective based on new materials of Ordolagus from Nei Mongol (northern China). Vertebrata Palasiatica, 2021, 59(2): 138-168.

图/表 9

Fig. 1 Geographical location of the fossil sites and temporal distribution of the taxa addressed in this paper relative to the Ulantatal Fm (Nei Mongol, northern China) A. location of Ulantatal and Saint Jacques; B. detail of location of Ulantatal and Saint Jacques (Google maps); C. landscape with fossil horizon Q1 in Saint Jacques; D. estimated chronological distribution of Ordolagus from Ulantatal and Saint Jacques (see Appendix I for details about the horizons and sections and their age estimation); the shaded area represents the chronological distribution of the genus Ordolagus basing on materials not yet studied in detail (ZZQ, IVPP); palaeomagnetic data from Wasiljeff et al. (2020); climatic data (blue arrows) from Sun and Windley (2015), Hauptvogel et al. (2017), Richoz et al. (2017), Ao et al. (2020) with references

Fig. 2 Gobiolagus tolmachovi and Ordolagus teilhardi from Nei Mongol, China A. Gobiolagus tolmachovi: left lower jaw, AMNH 26142, Nei Mongol, late Middle Eocene (Burke, 1941; Meng et al., 2005); B-J. Ordolagus teilhardi: B. left lower jaw, holotype, AMNH 20236;C. left lower jaw, IVPP V 26013.1; D. left lower jaw, V 26075.1; E. right lower jaw, V 26014; F. part of right lower jaw, V 26013.2; G. right lower jaw (juvenile), V 26017; H. left lower jaw, V 26012.2; I. right lower jaw, V 26012.1; J. left lower jaw, former paratype of O. teilhardi (not included in this review, MNHN, without formal inventory number; see Teilhard de Chardin, 1926:26, fig. 14C)

Table 1 Teeth measurements of Ordolagus from Nei Mongol, China (mm)

		p3			p4			m1			m2			m3
		L	W	L/W	L	W	Wtal	L	W	Wtal	L	W	Wtal	L	W	Wtal
Ordolagus teilhardi	AMNH 20236	2.05	2.27	0.90	2.08	2.77	2.02	2.37	2.91	2.27
	IVPP V 26012.1	1.93	2.35	0.82	1.93	2.60	2.05	2.25	2.80	2.00	2.50	2.88	2.33	1.58	1.90	1.05
	V 26012.2	1.87	2.36	0.79	2.05	2.72	2.00
	V 26013.1	1.90	2.33	0.82	2.03	2.68	1.93	2.55	3.18	2.15	2.75	3.10	2.50
	V 26013.2	2.05	2.29	0.90	2.05	2.43	1.76				2.55	2.91	2.12	1.10	1.62	0.83
	V 26014	2.16	2.40	0.90	1.85	2.70	1.90	2.23	3.06	1.91	2.20	3.12
	V 26015.1	1.88	2.20	0.85
	V 26015.2				1.80	2.75	2.05
	V 26015.3							2.20	2.85	2.13
	V 26017	1.57	1.71	0.92
	V 26017*	2.02*	2.31*	0.88
	V 26075.1	1.93	2.46	0.78	1.98	2.73	2.22
	V 26075.3	1.88*
	V 26075.4	2.10*
	V 26075.5	1.76*
	N	13	10	10	8	8	8	5	5	5	4	4	3	2	2	2
	Max	2.16	2.46	0.92	2.08	2.77	2.22	2.55	3.18	2.27	2.75	3.12	2.50	1.58	1.90	1.05
	Min	1.57	1.71	0.78	1.80	2.43	1.76	2.20	2.80	1.91	2.20	2.88	2.12	1.10	1.62	0.83
	Mean	1.93	2.27	0.86	1.97	2.67	1.99	2.32	2.96	2.09	2.50	3.00	2.31	1.34	1.76	0.94
OrdolagusMCD_1	V 6268.13	2.25	2.13	1.06	1.93	2.87	2.05	2.23	3.17	1.98	2.52	3.22	2.30
	V 26018.1	1.90	1.86	1.03	1.62	2.33	1.95
	V 26018.2	2.11?			1.62	2.52	1.71
	V 26019.1	2.27	2.09	1.08
	V 26019.2				1.75	2.54	1.60	1	1	1	1	1	1
	N	4	3	3	4	4	4
	Max	2.27	2.13	1.08	1.93	2.87	2.05
	Min	1.90	1.86	1.03	1.62	2.33	1.60
	Mean	2.14	2.03	1.06	1.73	2.57	1.83
OrdolagusMCD_2	V 6268.1	2.50	2.70	0.93	1.93	3.20	2.40	2.43	3.20	2.23	2.63	3.40	2.88
	V 6268.2	2.82	2.62	1.08	2.21			2.74	3.56	2.51
	V 6268.6	2.39?
	V 26016	2.36	2.64	0.89	1.90	2.90	2.14	2.50	3.14	2.24
	V 26020	2.36	2.30?	1.03?				2.26	3.19	2.14
	V 26021.1	2.57	2.51	1.02
	V 26021.2	2.38	2.43	0.98
	V 26021.3				1.86
	V 26021.4										2.38	3.26	2.19
	V 26022.1	2.50	2.35	1.06	2.15	3.45	2.48	2.61	3.85	2.50
	V 26023.1	2.59	2.49	1.04
	V 26023.2							2.56	3.25	2.54
	V 26023.3										2.72
	V 26024.1	2.19	2.17	1.01
	N	10	9	9	5	3	3	6	6	6	3	2	2
	Max	2.82	2.70	1.08	2.21	3.45	2.48	2.74	3.85	2.54	2.72	3.40	2.88
	Min	2.19	2.17	0.89	1.86	2.90	2.14	2.26	3.14	2.14	2.38	3.26	2.19
	Mean	2.47	2.49	1.00	2.01	3.18	2.34	2.52	3.37	2.36	2.57	3.33	2.53

Table 1 Teeth measurements of Ordolagus from Nei Mongol, China (mm)

		p3			p4			m1			m2			m3
		L	W	L/W	L	W	Wtal	L	W	Wtal	L	W	Wtal	L	W	Wtal
Ordolagus teilhardi	AMNH 20236	2.05	2.27	0.90	2.08	2.77	2.02	2.37	2.91	2.27
	IVPP V 26012.1	1.93	2.35	0.82	1.93	2.60	2.05	2.25	2.80	2.00	2.50	2.88	2.33	1.58	1.90	1.05
	V 26012.2	1.87	2.36	0.79	2.05	2.72	2.00
	V 26013.1	1.90	2.33	0.82	2.03	2.68	1.93	2.55	3.18	2.15	2.75	3.10	2.50
	V 26013.2	2.05	2.29	0.90	2.05	2.43	1.76				2.55	2.91	2.12	1.10	1.62	0.83
	V 26014	2.16	2.40	0.90	1.85	2.70	1.90	2.23	3.06	1.91	2.20	3.12
	V 26015.1	1.88	2.20	0.85
	V 26015.2				1.80	2.75	2.05
	V 26015.3							2.20	2.85	2.13
	V 26017	1.57	1.71	0.92
	V 26017*	2.02*	2.31*	0.88
	V 26075.1	1.93	2.46	0.78	1.98	2.73	2.22
	V 26075.3	1.88*
	V 26075.4	2.10*
	V 26075.5	1.76*
	N	13	10	10	8	8	8	5	5	5	4	4	3	2	2	2
	Max	2.16	2.46	0.92	2.08	2.77	2.22	2.55	3.18	2.27	2.75	3.12	2.50	1.58	1.90	1.05
	Min	1.57	1.71	0.78	1.80	2.43	1.76	2.20	2.80	1.91	2.20	2.88	2.12	1.10	1.62	0.83
	Mean	1.93	2.27	0.86	1.97	2.67	1.99	2.32	2.96	2.09	2.50	3.00	2.31	1.34	1.76	0.94
OrdolagusMCD_1	V 6268.13	2.25	2.13	1.06	1.93	2.87	2.05	2.23	3.17	1.98	2.52	3.22	2.30
	V 26018.1	1.90	1.86	1.03	1.62	2.33	1.95
	V 26018.2	2.11?			1.62	2.52	1.71
	V 26019.1	2.27	2.09	1.08
	V 26019.2				1.75	2.54	1.60	1	1	1	1	1	1
	N	4	3	3	4	4	4
	Max	2.27	2.13	1.08	1.93	2.87	2.05
	Min	1.90	1.86	1.03	1.62	2.33	1.60
	Mean	2.14	2.03	1.06	1.73	2.57	1.83
OrdolagusMCD_2	V 6268.1	2.50	2.70	0.93	1.93	3.20	2.40	2.43	3.20	2.23	2.63	3.40	2.88
	V 6268.2	2.82	2.62	1.08	2.21			2.74	3.56	2.51
	V 6268.6	2.39?
	V 26016	2.36	2.64	0.89	1.90	2.90	2.14	2.50	3.14	2.24
	V 26020	2.36	2.30?	1.03?				2.26	3.19	2.14
	V 26021.1	2.57	2.51	1.02
	V 26021.2	2.38	2.43	0.98
	V 26021.3				1.86
	V 26021.4										2.38	3.26	2.19
	V 26022.1	2.50	2.35	1.06	2.15	3.45	2.48	2.61	3.85	2.50
	V 26023.1	2.59	2.49	1.04
	V 26023.2							2.56	3.25	2.54
	V 26023.3										2.72
	V 26024.1	2.19	2.17	1.01
	N	10	9	9	5	3	3	6	6	6	3	2	2
	Max	2.82	2.70	1.08	2.21	3.45	2.48	2.74	3.85	2.54	2.72	3.40	2.88
	Min	2.19	2.17	0.89	1.86	2.90	2.14	2.26	3.14	2.14	2.38	3.26	2.19
	Mean	2.47	2.49	1.00	2.01	3.18	2.34	2.52	3.37	2.36	2.57	3.33	2.53

Fig. 3 Gobiolagus tolmachovi and Ordolagus teilhardi from Nei Mongol, China A. Gobiolagus tolmachovi: left lower jaw in labial view, AMNH 26142, Nei Mongol, late Middle Eocene (Burke, 1941; Meng et al., 2005); B-E. Ordolagus teilhardi: B. left lower jaw in labial (B1) and lingual (B2) views, holotype, AMNH 20236; C. right lower jaw in lingual (C1) and labial (C2) views, IVPP V 26012.1; D. left upper jaw in occlusal view, V 26013.3; E. right upper jaw in occlusal view, V 26012.3

Fig. 4 Camera lucida drawings of teeth of Ordolagus from Nei Mongol, China A-J. Ordolagus teilhardi: A. right p3-m3, IVPP V 26012.1; B. left p3-p4, V 26012.2; C. left p3-m1, V 26015.1-3; D. left p3-m1, V 26013.1; E. right p3-p4+m2-m3, V 26013.2; F. right p3-m2, V 26014; G1. right p3-m2, V 26017; G2. detail of p3 in lateral lingual view, V 26017; G3. detail of m2 in lateral lingual view, V 26017; H. left p3, V 26075.2; I. right p3, V 26075.3; J. detail of p3-p4 of left lower jaw, V 26075.1; K-M. Ordolagus MDC_1: K. left p3-m2, V 6268.13; L1. left p3-p4, V 26019.1, V 26019.2; L2. left p3 in lateral labial view, V 26019.1; M. right p3-p4, V 26018.1; N-V. Ordolagus MDC_2: N. right dp3, V 26022.2; O. left dp4, V 26022.3; P. right p3, V 26021.1; Q1. right p3-m2, V 6268.1; Q2. detail of p3 in lateral labial view, V 6268.1; R. left p3, V 26023.1; S. right p3, V 26024.1; T. right p3, V 26021.2; U. left p3, V 26020; V. left p3-m1, V 26022.1. Occlusal surfaces drawn parallel to the observer

Fig. 5 Length of p3 (in mm) of Ordolagus teilhardi (white diamonds), Ordolagus MDC_1 (grey diamonds) and Ordolagus MDC_2 (black diamonds)

Fig. 6 Length of the lower teeth (in mm) in Ordolagus teilhardi (white diamonds), Ordolagus MDC_1 (grey diamonds) and Ordolagus MDC_2 (black diamonds) The considered values are the maximum L values for each tooth position

Fig. 7 Ordolagus MDC_1 and Ordolagus MDC_2 from Nei Mongol, China A-C. Ordolagus MDC_1: A. left lower jaw in occlusal (A1) and labial (A2) views, IVPP V 6268.13; B. left lower jaw, V 26018.2; C. right lower jaw, V 26018.1. D-H. Ordolagus MDC_2: D. left lower jaw in occlusal (D1), labial (D2), and lingual (D3) views, V 26016; E. right lower jaw in occlusal (E1) and labial (E2) views, V 6268.1; F. left lower jaw, V 26020; G. left lower jaw, V 26022.1; H. right lower jaw, V 6268.6

Fig. 8 Size comparison between lower jaws of Ordolagus and other selected Eocene-Early Oligocene Asian lagomorphs A. Gobiolagus tolmachovi, AMNH 26142, left lower jaw with p3-m3, from Meng et al., 2005:4, fig. 1.1; B. Shamolagus grangeri, AMNH 26289, left lower jaw with p4-m3, from Meng et al., 2005:4, fig. 1.6; C. Desmatolagus gobiensis, AMNH 19102, right lower jaw with p3-m3, from Meng et al., 2005:4, fig 1.9; D. Ordolagus teilhardi, IVPP V 26012.1, right lower jaw with p3-m3

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