RESTUDY OF FOSSIL SPECIMENS OF GENUS SINAECHINOCYAMUS (ECHINOIDEA; CLYPEASTEROIDA) WITH NEW OCCURRENCES FROM TAIWAN

1. Restudy of fossil specimens of genus
Sinaechinocyamus (Echinoidea; Clypeasteroida)
with new occurrences from Taiwan
Wei‐Chia Chu
Central Geological Survey, MOEA.
Zhonghe Dist., New Taipei City, Taiwan.
vegachu@moeacgs.gov.tw
Session: New Advances on Stratigraphy and Paleontology in Taiwan

2. Introduction
• The genus Sinaechinocyamus (Echinoidea:
Clypeasteroida) is a group of small sand dollar. Adults
are generally about one centimeter in diameter.
• Due to its small size, it was often mistaken for the
larva of another species of sand dollars.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

3. Introduction
• SYSTEMATICS
Class Echinoidea Leske, 1778
Order Clypeasteroida A. Agassiz, 1872
Suborder Scutellina Haeckel, 1896
Family Taiwansteridae Wang, 1984
Genus Sinaechinocyamus Liao, 1979
Species Sinaechinocyamus planus Liao, 1979
Sinaechinocyamus mai (Wang, 1984)
Sinaechinocyamus pitouensis (Wang, 1984) †
Sinaechinocyamus gutingkengensis (Wang, 1984) †
(fossil species with † mark)
Session: New Advances on Stratigraphy and Paleontology in Taiwan

4. Introduction
• Based on the author’s field investigations and reports
from amateur collectors, there are more and more
fossil localities of Sinaechinocyamus are known in
Taiwan in recent years. At least 10 sites (8 of them
are visited and new fossils are collected by the
author).
• Goals of study are to compare and contrast samples
from 8 fossil and one modern localities with linear
measurements, and to find out how many species
are present in studied samples.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

5. Materials
• In this study, a total of 321 fossil and
extant specimens of genus
Sinaechinocyamus were collected from
9 sites (8 sites are fossil specimens, 1
site is extant specimens) for analysis
and discussion.
Session: New Advances on Stratigraphy and Paleontology in Taiwan
Sample localities :
(1) Bitoujiao, (2) Sanying Bridge, (3) Longgang,
(4) Niupu, (5) Jhonglung, (6) Niushan,
(7) Guanzjling, (8) Dongyuping, (9) Gutingkeng,
(10) Zengwenxikou(extant specimens).

6. Materials
Specimens of Sinaechinocyamus
from different localities:
1 and 2: Sanying Bridge
3: Longgang
4: Niupu
5: Jhonglung
6: Guanzjling
7: Dongyuping
8 and 9: Zengwenxikou
In every location, a: aboral view, b:
oral view, c: posterior lateral view.
White bar = 5 mm.
*Specimens in Bitoujiao, Jhonglung,
and Niushan were studied on‐site
because that fossil‐bearing
sandstones are cemented very well
and cannot be collected.
**Specimens in Gutingkeng is only
reported by Wang(1984).
Session: New Advances on Stratigraphy and Paleontology in Taiwan

7. Methods
1. Sample site analysis
Session: New Advances on Stratigraphy and Paleontology in Taiwan
Location Area Stratigraphy Age
(1)Bitoujiao Rueifang Dist., New
Taipei City
Kueichuling Formation,
Erhchiu Member
Early Pliocene
(2)Sanying Bridge Sanxia Dist., New Taipei
City
Kueichuling Formation,
Tapu Member
Late Miocene
(3)Longgang Houlong Township,
Miaoli County
Toukoshan Formation Middle Pleistocene
(4)Niupu Jhongpu Township,
Chiayi County
Kanshialiao Formation Early Pleistocene
(5)Jhonglun Jhongpu Township,
Chiayi County
Yunshuichi Formation Late Pliocene
(6)Niushan Dongshan Dist., Tainan
City
Liuchungchi Formation Late Pliocene
(7)Guanzjling Baihe Dist., Tainan City Yunshuichi Formation Late Pliocene
(8)Dongyuping Wangan Township,
Penghu County
Recent beach deposits Holocene
(9)Gutingkeng Tianliao Dist.,
Kaohsiung City
Gutingkeng Formation Late Pliocene
(10)Zengwenxikou Cigu Dist., Tainan City Beach deposits Recent

8. Methods
2. Statistical analysis:
• Test length (L), test width (W), and test
height (H) of each specimen were measured.
• In the Linear Regression Analysis of the data,
the regression equation can be expressed as
Y = aX+b. Where X is independent variables,
Y is dependent variables, a is the slope of the
regression line, and b is the intercept of the
regression line on the Y axis.
• Test length (L) is set as the independent
variable (X); the test width (W) and test
height (H) are set as the dependent variables
(Y) to discuss its changes in the growth
process.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

9. Results
• From the perspective of fossil
ages, Sinaechinocyamus may
have appeared in the northern
part of Taiwan since the late
Miocene, and gradually
distributed to the southern
Taiwan in the late Pliocene.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

10. Results
• Measurements from 5 locality.
• Bivariate plots of Sanying Bridge section are based on 28 complete samples.
The largest sample L=7.50mm, W=7.80 mm, H=1.55 mm. The smallest
sample L=2.65mm, W=2.60 mm, H=0.70 mm.
• Bivariate plots of Longgang section are based on 57 complete samples. The
largest sample L=10.98mm, W=10.55 mm, H=2.57 mm. The smallest sample
L=3.95mm, W=3.80 mm, H=1.45 mm.
• Bivariate plots of Niupu section are based on 42 complete samples. The
largest sample L=6.50mm, W=6.70 mm, H=1.45 mm. The smallest sample
L=2.60mm, W=2.60 mm, H=0.70 mm.
• Guanziling data(Chu, 2003) are based on 42 complete samples. The largest
sample L=6.13mm, W=6.35 mm, H=1.30 mm. The smallest sample
L=2.18mm, W=2.12mm, H=0.64 mm.
• Zengwenxikou data(Chu, 2003) are based on 62 extant complete specimens.
The largest sample L=7.65mm, W=7.85 mm, H=1.70 mm. The smallest
sample L=2.75mm, W=2.85 mm, H=0.65 mm.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

11. Results
• By combining all fossil data
from four localities and
modern samples from one
locality, the W/L ratios
between populations and
overall population are very
similar.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

12. Results
• The H/L ratios exhibit similar
results.
• In summary, among 231
samples analyzed, fossil and
living samples are
indistinguishable.
• They should all be identified
as S. mai.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

13. Discussions
• Results of linear regression analyses derived from
samples collected from five locations (Sanying B.,
Longgang, Niupu, Guanziling, and Zengwenxikou
sections) show that the S. mai test length is slightly
larger than the test width.
• Mooi (1990) compared the extant species of S. planus
and S. mai, and found that they are very similar in size
and shape. The difference lies in the ratio of test
width to length, in which the W/L ratio is about 0.909
in S. planus and about 1.052 in S. mai.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

14. Discussions
• Sinaechinocyamus is first put under the Order
Clypeasteroida by Wang(1984). According to recent
morphological and molecular studies,
Sinaechinocyamus now is placed in Order
Scutelloida(Kroh, 2020; Mongiardino Koch and
Thompson, 2021).
So:
Class Echinoidea Leske, 1778
Order Clypeasteroida A. Agassiz, 1872  Scutelloida Mongiardino Koch et al., 2018
Suborder Scutellina Haeckel, 1896 Infraorder Scutelliformes Haeckel, 1896
Family Taiwansteridae Wang, 1984
Genus Sinaechinocyamus Liao, 1979
Session: New Advances on Stratigraphy and Paleontology in Taiwan

15. Conclusions
• In summary, fossil occurrences of Sinaechinocyamus
range from Tapu Member of Kueichulin Formation
(late Miocene) to Toukoshan Formation (Pleistocene)
in Taiwan .
• Among the fossil localities in Taiwan, there is no
obvious difference between the samples and within
the sample. More specifically, fossil data and modern
samples of S. mai are indistinguishable. Thus, all
fossil samples reported here should be treated as S.
mai.
Session: New Advances on Stratigraphy and Paleontology in Taiwan

16. References
• Chu, W. C., 2003: Study of the Small Clypeasteroid Echinoids Fossils from
Kuantseling, Tainan. Master's thesis of Department of Earth sciences,
National Cheng Kung University, 59pp.
• Kroh A. 2020: Phylogeny and classification of echinoids. In: Lawrence J.M.,
editor. Sea urchins: biology and ecology. 4th ed. Cambridge: Academic Press,
1–17.
• Liao, Y., 1979: A new genus of clypeasteroid sea‐urchin from Huang Hai.
Oceanologia et Limnologia Sinica, 10(1), 67‐74.
• Mongiardino Koch, N. and Thompson, J. R., 2021: A total‐evidence dated
phylogeny of Echinoidea combining phylogenomic and paleontological data.
Syst. Biol. 70(3), 421–439.
• Mooi, R., 1990: Progenetic miniaturization in the sand dollar
Sinaechinocyamus: implications for clypeasteroid phylogeny: C. De Ridder, P.
Dubois, M.‐C. Lahaye, M. Jangoux (Eds.), Echinoderm Research: Proceedings
of the Second European Conference on Echinoderms, A. A. Balkema, Brussels,
Belgium, 18–21 September, 1989 (1990), 137‐143.
• Wang, C. C., 1984: New classification of Clypeasteroid echinoids. Proc. Geol.
Soc. China, 27, 119‐152.
Session: New Advances on Stratigraphy and Paleontology in Taiwan