部分粗菊石 Trachyceratidae

Sirenites（Sirenitinae） vs  Yakutosirenites（ Arpaditinae）

美女神菊石属 vs  雅库特美女神菊石属

All ammonoids assigned in this paper to the genus Sirenites have a compressed discoconic shell with moderately embracing whorls overlapping approximately half of the height of the preceding whorl.  The ornamentation on the flanks is composed of densely spaced crescentic ribs with five spirals of nodes:umbilical, two lateral, ventrolateral, and ventral.  The ribs begin from the umbilical shoulder and terminate with the nodes of the ventral spirals;  they tend to expand toward the venter.  This feature was already mentioned in the first description of the senticosi group (Mojsisovics, 1893, p. 727).  The ventrolateral spiral of nodes lying on the ventral shoulder, the ribs split into two shorter ribs, sharply bent forward and reaching the ventrolateral spiral of nodes.  The splitting is observed at the middle and later growth stages (shell diameter more than 10−15 mm), either in every second rib or in each rib, so the number of nodes of the ventral spiral is 1.5–2 times higher than that of the ventrolateral spiral.  The ribs, unlike in the genus Yakutosirenites, are maintained at the later growth stages(Plate I, figs.  3, 8). On either side of the midventral groove, there are either raised keels with elongated frequently spaced oblique nodes of ventral spirals (Plate I,fig.  1c) or densely spaces pointed carinate nodes, lowering toward the groove (Plate I, fig. 2c).

本文所确定的Sirenites菊石属都有一个压缩的盘状壳，其螺旋高度约为前一螺旋高度的一半。侧翼的纹饰由密集间隔的新月形肋组成，肋上有五个螺旋状结节:脐部的、两个侧面、腹侧部和腹部。肋从脐肩开始，终止于腹部螺旋结节;它们倾向于向腹部扩张。这一特征已经在第一次描述senticosi群时被提及(Mojsisovics, 1893, p. 727)。腹侧部螺旋状结节位于腹肩部，肋分裂为两根较短的肋，急前弯，并到达腹侧部螺旋状结节。在生长的中后期(壳直径大于10 ~ 15 mm)，要么是每隔一个肋要么是在每一肋都有分裂，因此腹部螺旋的结节数是腹侧部螺旋的1.5-2倍。与Yakutosirenites属不同的是，肋在生长后期保持不变(Plate I, figs. 3, 8)。在腹中沟的两侧，要么有凸起的脊，并有伸长而常间隔的腹部螺旋斜节(Plate I,fig.  1c)，或密集的、向凹槽降低的空间指向隆凸的结节(Plate I，fig 2c)。

 In the shape of the nodes of the ventral spiral, this ammonoid group is readily distinguished from the genus Yakutosirenites, in particular, from Y. pentastichus (Vozin), in which the ventral spiral possesses widely spaced large spines, when the shell matrix is preserved (Plate I,fig. 6a), and on the mold, rounded, elongated ridges(Plate I, figs. 4a, 4b).  

在腹部螺旋结节的形状上，Sirenites很容易与Yakutosirenites属区分开来，特别是与Y. pentastichus (Vozin)区分开来。当后者壳的母体被保存下来时，可以看到外旋环腹部螺旋拥有宽间隔的棘状突起 (Plate I,fig.   6a)，并在体型上，有圆形，细长的脊(Plate I, figs.   4a, 4b)。

Plate I. Ammonoids of the genera Sirenites and Yakutosirenites from the lower–upper Carnian boundary beds of Northeast Asia (northern Verkhoyansk Region, Darky River; northern Okhotsk Region, Vtoraya Sentyabrskaya River; Kotelnyi Island, Tikhaya River). In all cases: (a) lateral view, (b) apertural view, (c) ventral view. All sizes are natural, except for the specially mentioned cases. The collection of illustrated ammonoids is housed in the Monographic Department of Central Siberian Geological Museum (TsSGM) in the Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk), coll. no. 2080. (1, 8) Sirenites ovinus Tozer, lower Carnian, upper part of the armiger Zone−lower Carnian, lower part of the pentastichus Zone: (1) specimen no. 1/2080, northern Okhotsk Region, basin of the Yana Okhotskaya River, Vtoraya Sentyabrskaya River, Outcrop C-2, Bed 3, 2 m above the base; (8) specimen no. 6/2080; northern Verkhoyansk Region, Darky River, Outcrop 52, Bed 8, 3.5 m above the base; (2, 3) Sirenites senticosus (Dittmar), lower Carnian, armiger Zone: (2) specimen no. 2/2080, ×3, Kotelnyi Island, Tikhaya River, loc. 06-8, Bed 4, 11 m above the base; (3) same specimen put together with the subsequent whorl in argillaceous limestone with small ammonoids; dashed lines indicate specimens and imprints of Yakutosirenites armiger (Vozin) sp. juv.; solid arrows show Sirenites senticosus (Dittmar) sp. juv; (4–6) Yakutosirenites pentastichus (Vozin), lower Carnian, pentastichus Zone: (4) specimen no. 3/2080, northern Okhotsk Region, basin of the Yana Okhotskaya River, Vtoraya Sentyabrskaya River, Outcrop С-2, Bed 3, 4.5 m above the base; (5) the same specimen, ×3; (6) specimen no. 4/2080, in a clayey-carbonate concretion, the same locality, Bed 3; 8.7 m above the base; (7, 11, 12) Sirenites sp. indet., lower Carnian, armiger Zone: (7) specimen no. 5/2080, Kotelnyi Island, Tikhaya River, loc. 06-8, Bed 4; 5 m above the base; (11) specimen no. 9/2080, northern Okhotsk Region, basin of the Yana Okhotskaya River, Vtoraya Sentyabrskaya River, Outcrop С-2, Bed 1; 40.5 m above the base; (12) specimen no. 10/2080, (12a and 12b) lateral views, the same locality, Bed 1; 43.5 m above the base; (9) Sirenites cf. senticosus (Dittmar), lower Carnian, armiger Zone, specimen no. 7/2080, northern Verkhoyansk Region, Darky River, Outcrop 52, Bed 7; 4 m above the base; (10) Striatosirenites cf. dromas (Dittmar), photograph from a latex cast, lower Carnian, armiger Zone, specimen no. 8/2080, northern Verkhoyansk Region, Darky River, Outcrop 52, Bed 8; 2.5 m above the base.

参考：The Yakutosirenites armiger Ammonoid Zone of Northeast Asia as a Reference Level of the Boreal-Tethyan Correlation of the Lower Carnian.

前粗菊石属 Protrachyceras

壳体半内卷至近内卷，呈扁饼状。腹部具腹沟,沟旁各有一排瘤。壳表具有许多横肋,每一肋上附有排列规则的瘤,横肋常分叉或插入。缝合线为亚菊石式，鞍部也发生微弱的褶皱。

粗菊石属 Trachyceras Mojsisovics，1893

壳体半外卷到近内卷，厚饼状到扁饼形。腹部穹圆，有明显腹中沟，两旁的腹棱上有两排瘤。侧面饰有简单的、二分的、微弯的肋纹。肋上有若干排成旋转状的瘤节。缝合线为亚菊石型，每一外侧面有两个分齿不很长的侧叶。

对比：前粗菊石的腹沟两旁的棱上只有一排瘤，其为两排。

副粗菊石属 Paratrachyceras Arthaber, 1914

亚科：Protrachyceratinae

The whorl section is compressed with broadly arched flanks which bear flat ribs that project forward near the venter. The ribs are much broader than the interrib spaces. The ribs cross the venter forming  forward projected chevrons within a ventral  furrow. The ribs are broadest near the ventral region of the flanks and narrow slightlywhere they are projected forward and over  the venter. 

Remarks：As well as one can interpret  these specimens, the main morphological features-that is the compressed whorl section, degree of involution, the nature of the ribs, the absence of nodes or tubercles and the grooved venter-indicate affinities to Trachyceras (Paratrachyceras). In most species of this genus the ventral groove is smooth, the ribs not crossing the venter. The only exception to this that I have been able to  discover is the specimen described and illustrated by Arthaber (1914, p. 137, pl. 16,  fig. 1) as T. (Paratrachyceras) regoledanum (Mojsisovics) from an Upper Ladinian horizon in Turkey.  This specimen has the ribs passing over the venter in the same fashion as that of the Thailand specimen illustrated here on figures 1,2.  Arthaber's  specimen appears to be quite similar to the Thailand specimens in terms of conch shape, involution, and type of ribbing except that there are some nodes on the ribs. Other illustrations of this species, unfortunately, do not show the nature of the venter.

旋环部分被宽拱的侧翼压缩，侧翼支撑着靠近腹部前伸的扁平肋。肋比肋间隙宽得多。肋穿过腹面，在腹面沟槽内形成向前投影的v形。肋在侧翼的腹侧区域附近最宽，在向前突出并于腹部的地方略微狭窄。

备注: 除了可以解释这些标本外，主要的形态学特征——压缩的旋环、内卷程度、肋的性质、没有nodes或tubercles以及有具沟的腹部——表明与Trachyceras (Paratrachyceras)有亲缘关系。在本属的大多数种的腹沟是光滑的，肋不穿过腹部。所能发现的唯一例外是Arthaber (1914, p. 137, pl. 16，图1)描述和说明的来自土耳其上拉底地区地平线的T. (Paratrachyceras) regoledanum (Mojsisovics)标本。这个标本的肋穿过腹部的方式与figures 1,2.所示的泰国标本相同。Arthaber的标本在壳形、内卷和肋类型方面似乎与泰国的标本非常相似，除了肋上有一些nodes。不幸的是，这个物种的其他插图并没有显示腹部的性质。

奥地利粗菊石属  Austrotrachyceras

亚科：Trachyceratinae

None show suture lines. All show two spirals of tubercles adjacent to the ventral sulcus flanked by a smooth band. Clearly shown is the principal generic character of Austrotrachyceras, namely feeble projection of growth lines and tubercle spirals on the venter.

没有显示缝合线。所有图均显示两螺旋状排列的结节毗邻腹沟，腹沟两侧有平滑带。主要的一般特征，即生长线和结节螺旋在腹部上的微弱突起被清楚地显示。

参考：CANADIAN TRIASSlC ANlMONOID FAUNAS，1994