共查询到17条相似文献，搜索用时 31 毫秒
1.
2.
3.
本文记述的是在云南禄丰腊玛古猿化石产地发现的原猴类化石,分类上归于兔猴科。鉴于它的形态特征,作者把它订为一新属新种(Sinoadapis carnosus gen. et sp. nov.),这是迄今已知兔猴科最晚的记录。这一发现对兔猴类的进化及探讨腊玛古猿的生活环境具有一定的意义。 相似文献
4.
本文记述了在云南禄丰盆地下上新统石灰坝组下部和中部两个三趾马化石层中发现的象类化石,包括四棱象属一未定种、轭齿象属一新种和嵌齿象属一未定种,它们都是云南地区早上新世腊玛古猿—三趾马动物群中的重要成员,在生物学和地层学上有一定的意义。 相似文献
5.
格沙头期的窃果猴类(carpolestid)孟氏苏崩猴(Subengius mengi)属于亚洲已知最早的近兔猴形类(plesiadapiform)。苏崩猴的新标本澄清了该类群的牙齿解剖结构。孟氏苏崩猴的齿列比以前认为的要原始得多,下齿列的齿式2.1.3.3,p4低冠,具有3个主尖,但不似Elphidotarsius的相应主尖那样完全并生,P3的舌侧缘更窄,结构更简单,m1不具有高度扩展的下前尖和下后尖。苏崩猴P3的独特结构以及对Elphidotarsius sp.,cf.E.florencae的P3解剖特征的重新研究表明,过去对窃果猴科P3的某些齿尖的同源性的解释是错误的。在详细的特征分析基础上,重新建立了窃果猴类及其近亲的系统发育关系。崩班期(Bumbanian)的同时猴(Chronolestes simul)被重新认定是窃果猴科最基部的成员。孟氏苏崩猴以及崩班期的另一个种旭日多脊食果猴(Carpocristes oriens)也是窃果猴类相对靠基部的成员,但这些亚洲窃果猴类之间似乎都没有特殊的相互关系。虽然北美和亚洲的窃果猴类均延续到古新世-始新世界线附近,但它们在两个大陆之间的扩散似乎仅限于古新世的较早期。 相似文献
6.
7.
检测了卵胎生入侵种食蚊鱼(Gambusia affinis)繁殖期个体大小和形态特征的两性异形以及雌性繁殖输出。结果表明,繁殖期,雌性个体的数量显著大于雄性个体,雌性个体的体长显著大于雄性个体,食蚊鱼属于偏向雌性的两性异形。以体长为协变量的One-way ANCOVA及后续的Tukey's检验显示,特定体长食蚊鱼的雌性个体的头宽、眼间距、体宽和体重均显著大于雄性个体;头长和尾鳍长的两性间差异不显著。6个形态特征变量的主成分分析(Eigenvalue≥1)发现,前2个主成分共解释65.1%的变异。头宽、眼间距、体宽和体重在第一主成分有较高的正负载系数(解释45.4%变异),头长在第二主成分有较高的负负载系数(解释19.7%变异)。食蚊鱼的繁殖输出与母体个体大小的线性回归显示,窝仔数和窝仔重均与母体体长、体重呈显著的正相关;食蚊鱼的繁殖输出与母体局部特征的线性回归显示,窝仔数和窝仔重均与母体头宽、眼间距和体宽呈显著的正相关。窝仔数与后代个体的平均体长呈显著的正相关、与后代个体的平均体重相关不显著,后代个体大小与数量不发生权衡。食蚊鱼繁殖期的性别比例、个体大小和局部形态特征的两性异形受生育力选择、性选择、生态位分化、食物竞争等多种选择压力的作用,也有利于该物种种群扩张和快速入侵。 相似文献
8.
中国石龙子个体发育过程中头部两性异型和食性的变化 总被引：10，自引：1，他引：10
许多动物呈现个体大小、局部形态特征 (头部大小 )和体色的两性异形[5,14 ,15,2 1,2 2 ] 。 Darwin[12 ] 认为两性谋求各自最大的繁殖利益导致了两性异形 ,因此两性异形是性选择压力作用的结果。自 Darwin以来 ,许多同行认为性选择压力和非性选择压力均能导致动物的两性异形 ,两种选择压力在不同的动物中所起的作用是不同的 [2～ 5,7,10 ,16,2 1～ 2 6] 。性选择压力导致的两性异形与繁殖成功率直接有关。非性选择压力导致的两性异形与繁殖成功率无关或无直接的关系 ,如两性寿命的差异 [13 ]、两性食性的分离 [6,2 1]和两性分配用于生长的… 相似文献
9.
测定了乐山棒花鱼(Abbottina kiatingensis)繁殖期形态特征包括体长、头长、头宽、头高、吻长、眼后头长、眼径、眼间距、体高、尾柄长、尾柄高、尾鳍长、背鳍基前距、背鳍基长、腹鳍基前距、腹臀间距、体重和去内脏体重的两性异形和雌性个体生育力。繁殖期雄性个体的数量显著多于雌性个体,雌雄两性个体的体长差异不显著。特定体长的雌性个体的头长、头宽、头高、吻长、眼后头长、尾柄高、背鳍基前距、背鳍基长和去内脏体重显著小于雄性个体,其余指标不存在明显的差异。回归分析表明,乐山棒花鱼的怀卵数量与体长和体重回归关系显著,雌性通过个体大小(体长和体重)的增加来提高个体生育力。 相似文献
10.
棒花鱼形态特征的两性异形和雌性个体生育力 总被引：6，自引：0，他引：6
测定了棒花鱼(Abbottina rivularis)繁殖期形态特征包括体长、头长、头宽、头高、眼间距、鼻间距、背鳍基长、胸鳍长、胸鳍腹鳍间距、尾柄长、尾鳍长和体重的两性异形和雌性个体生育力。结果表明,雄性个体的数量显著多于雌性个体,雄性个体的体长显著大于雌性个体。特定体长的雌性个体的胸鳍腹鳍间距显著大于雄性个体,头长、头宽、头高、眼间距、鼻间距、背鳍基长、胸鳍长、尾柄长和尾鳍长显著小于雄性个体,雌雄两性体重不存在显著差异。棒花鱼的怀卵数量与体长和体重回归关系显著。偏相关分析显示,当控制第三者恒定时,怀卵数量与体长和体重呈正相关但不显著。棒花鱼存在个体大小和其他局部特征显著的两性异形,雌性个体主要通过腹腔容积的增加提高个体生育力。棒花鱼形态特征的两性异形是性选择和生育力选择共同作用的结果。 相似文献
11.
The diagnostic characters of the two species in Sinoadapis described previously in Lufeng specimens have been observed to be continuous through transitional phenotypes and the combinations of characters of the two species exist in some specimens. These characters are hereby not of taxonomic value but variations within a single species. Therefore, Sinoadapis shihuibaensis is considered to be a synonym of Sinoadapis carnosus and should be sunk. Sinoadapis in Lufeng is treated as a genus of single species.<br>The diagnostic characters which distinguish Sivaladapis from Indraloris from the Siwaliks of India and Pakistan art analogous to those for distinguishing the two “species” of Sinoadapis. It is believed that the “gap” between the two genera would be filled by specimens which have not been discovered yet. It is probable that they may be a synonymous genus or even species.<br>The distributions of each dimension of upper and lower canines in Sinoudapis are sexually non-overlapping with the exception of upper canine breadth probably due to the small sample size. Consequently, the canine specimens are easily sexed. As a measure of canine size dimorphism, the male/female ratio for a single dimension is determined to be 1.2.<br>Unlike the canines, the distributions of each dimension of the lower 4th premolars are sexually overlapping or sexually non-discriminating, Nevertheless, the bi-dimensional distribution of length and breadth of the teeth reveals to some extent the existence of two clusters with few intermediates in the area of both means in sexually pooled sample. The concentrations represent the male and female averages of the measurements concerned respectively. The size dimorphism of the lower 4th premolars estimated by this way bas a ratio of 1.08. If this ratio is representative of the extent of generalized body dimorphism in one dimension, the male/female ratio of body weight might be estimated to be 1.26, or 8kg for male average and 6.4 kg for female average. 相似文献
12.
Pan Yuerong 《人类学学报》1986,5(01):31
The paper deals with a new form of Sinoadapis from the Lufeng hominoid Locality, assigned to Sinoadapis shihuibaensis sp. nov. .<br>Holotype<br>PA 882 A fragment of right mandible with C, —M3.<br>Other materials<br>PA 903 A fragment of left maxilla with P3—M3.<br>PA 959 Left lower tooth row with I1—P2, P4.<br>PA 902 Right upper tooth row with C'-p3.<br>PA 964 An isolated left I1. PA 907 An isolated right I2.<br>PA 972 An isolated right M3.<br>In comparison with Sinoadapis carnosus the new species shows the following features: relatively slender mandible with narrower cheek teeth, sharper cusps, larger trigonid fovea, developed buccal cingulum and larger upper and lower canines. The hypoconulid is elongated posteriorly and is separated from the entoconid by a deep notch. The buccalingual diameters of upper molars are slightly smaller and the lingual cingula are rather developed. The metaconid is relatively reduced in M3 and the metacone located relatively closer to the protocone.<br>Sinoadapis differs from Sivaladapis principally in its larger size and the P4 highly molarised and longer than any molar of the same individual. A series of upper and lower dentitions of Sinoadapis shihuibaensis were preserved. Sinoadapis shihuibaensis is basically similar to that of Sivaladapis nagri described by Gingerich. However, it also differs from Sivaladapis nagrii in some characters. The lingual cingula incompletely enelose the protocone in upper fourth premolar and upper molars and there are no enamel folds in the lingual wall of the protocone. The upper and lower third prenolars are narrower? Both the trigonid and the talonid in P4 are enlarged and the large pro- toeone located more forward than the metaconid. There are clear demarcations between the cusps, but no the enamel folds on the lingual surface. The lower molars have large trigonid fovea. The notch between the hypoconulid and the entoconid is not as deep as Sivaladapis nagrü, while the cusps of Siraladapis nagri are sharper than that of Sinoadapis shihuibaensis.<br>Adapid primates of Lufeng are more abundant than those of both India and Pakistan and the species frum Lufeng seems to be more complex. It indicates that there is probably a major radiation of Mioeenp adapids in Lufeng. Sinoadapis of Lufeng elearly differs from both Indraloris and Siralapis from the Siwaliks of India and Pakistan. Judging from the Lufeng mammalian fauna, Lufeng hominoid site is younger in age than Nagri beds near Haritalyangar of India. The Lufeng speeies provides important. fossil evidence for the understandinr of Miocene Adapids. 相似文献
13.
Two fragments of mandible, one left with P4—M2 and the other right with M1-M3, of the same individual (PA 885, holotype) , assigned to a new form of adapid, Sinoadapis carnosus gen. et sp. nov. were described in this paper.<br>About 380 specimens of this form including 48 maxillas and mandibles, 260 isolated teeth and 75 tooth rows, were collected from Lufeng, Yunnan. 60 per cent of them were unearthed from Layer II of Section D.<br>Diagnosis of the new genus: An Asian Miocene adapid primate, larger than that of either Sivaladapis or Indraloris. The lower fourth premolar is highly molarised and longer than any molar of the same individual. A distinct hypoconulid twinned with the entoconid, with a deep notch between them, is found in the lower fourth premolar and the buccal cingulum is weakly developed. The lower molars are short and broad. There is no cingulum on the buccal side. The buccal cingulum is present only on the distal side of the crown. The crowns are low and round.<br>Sivaladapis and Indraloris are two sufficiently similar genera. Some specimens of Indraloris have been attributed to Sivaladapis by Gingerich. As a result, only a few specimens represent Indraloris. Some features of the two genera ean also be seen in our specimens. According to Chopra, it seems not easy to distinguish Indraloris from Sivaladapis, so it is not impossible that they are of the same genus.<br>Sinoadapis carnosus gen. et sp. nov. from Lufeng is the latest record in late Miocene. This diseovery indicates that the final extinction of Adapidae may be later than the end of Miocene (8 Myr-) and it is helpful to the study of the natural environment of Ramapithecus. 相似文献
14.
蜘蛛的性二型现象及其进化 总被引：1，自引：0，他引：1
对蜘蛛的性二型现象进行了初步的概括,并试图以食物对种群繁衍的影响为线索说明其进化机制。蜘蛛的性二型现象主要表现在体形大小上,一般雌性大于雄性;食物的数量和分布制约着蜘蛛性二型现象的进化。 相似文献
15.
16.
The Japanese filefish Paramonacanthus japonicus has extreme sexual dimorphism in its overall shape, even though its mating system is monogamy with biparental care. This
sexual dimorphism is mainly due to the development of secondary sexual traits in males. Males become more slender in body
with elevated soft dorsal and anal fins as they mature. We examined the function of such male secondary sexual traits by field
research and fluid-dynamic analysis. Underwater observations showed that movement rate and steady swimming speed of males
were higher than those of females. Male and female P. japonicus showed similar feeding habits and egg-tending behavior, although males attacked potential egg predators more frequently.
A wind-tunnel experiment using the air bearing and spring system showed that the drag coefficient of males was significantly
lower than that of females, indicating a lower male hydrodynamic drag performance. Also, male elevated soft dorsal and anal
fins are considered to give rise to higher thrust performance in monacanthids. Thus, these results suggest that male secondary
sexual traits are hydrodynamic devices for enhancing swimming performance that seem to be actually functional under natural
conditions. We discuss the evolution of such conspicuous male sexual traits in P. japonicus.
Electronic Publication 相似文献
17.
The estuarine grapsid crabs Chasmagnathus granulata and Cyrtograpsus angulatus belong to the most typical and dominant inhabitants of brackish coastal lagoons in southeastern South America. In a combined laboratory and field investigation of juvenile growth, we measured the increase in body size in these species under controlled conditions as well as in field experiments (in Mar Chiquita lagoon, Argentina), seasonal changes in size frequency distribution of a natural population, and growth related changes in selected morphometric traits of male and female juveniles (relations between carapace width, carapace length, propodus height and length of the cheliped, and pleon width). At 24°C, Cy. angulatus grew faster than Ch. granulata; it reached the crab-9 instar (C9; 13 mm carapace width) after 92 days, while Ch. granulata required 107 days to reach the C8 instar (7.4 mm). At 12°C, growth ceased in both species. The pleon begins to show sexual differences in the C5 (Cy. angulatus) and C8 instar (Ch. granulata), respectively, while the chelae differentiate earlier in Ch. granulata than in Cy. angulatus (in C4 vs C6). In the field, growth was maximal in summer, and was generally faster than in laboratory cultures. However, there is great individual variability in size (about 25% even in the first crab instar) and in size increments at ecdysis, increasing throughout juvenile growth. Our data indicate that, in the field, small-scale and short-term variations in feeding conditions, temperature, and salinity account for an extremely high degree of variability in the absolute and relative rates of growth as well as in the time to sexual differentiation. Received in revised form: 20 September 2001 Electronic Publication 相似文献