A NEW FOSSIL SPECIES OF THE GENUS HONGKONGITES FROM TOLO CHANNEL FORMATION:

TAXONOMICAL REVIEWS OF H. hongkongensis & H. liberalis sp. nov.

 We would like to dedicate to the pioneers who have contributed to the study of Hongkonites,

also pay tribute to Hong Kong people in misery.

 Owen et E. Ng

  Cognitio Sapiens Ngensis, Acta Scientrium Ngensis,
  Email address:  hongkongites@gmail.com

CHINESE VERSION       MAIN        AETAS GEOLOGICA HONGKONGICA (Chinese)

ABSTRACT
New finds of Hongkongites fossils helps to solve of taxonomical problems and restore the status of genus Hongkonites, a detailed information of Hongkongites hongkongensis Grabau, 1923 is included and the conceived reconstruction of their suture lines, and also describes a new species Hongkongites liberalis Ng et al., 2020.   

KEY WORDS
Hongkongites hongkongensis Grabau, 1923, Genus Hongkongites, Family: Schlotheimiidae, Tolo Channel Foramtion (Nai Chung area, Fung Wong Wat area, seashore area of Pak Kok Chai, Northern New Terrorities, Hong Kong), Early Jurassic (196.5~189.6 Ma) .

STRATIGRAPHY OF THE LOCALITIES

Map of geographic range: Tolo Channel Formation

Landforms of Tolo Channel Formation (1. Nai Chung, 2.Ma Shi Chau, 3.Sham Chung, 4.Sea Shore of Tolo Channel,  5.Fung Wong Wat,  6.Seashore of Pak Kok Chai),  7. Tai Tong, Yuen Long (Not investigated)

The Tolo Channel Foramtion of early Jurassic age (196.5Ma ~ 189.6Ma)[1] consists of of grey laminated siltstone with interbedded fossiliferous black mudstone, it is confined to narrow exposures on Nai Chung, Ma Shi Chau. Sam Chung, Fung Wong Wat area and seashore area of Pak Kok Chai on the both side of Tolo Channel, in Northern New Terrorities, Hong Kong. Since a pebbled-liked Hongkongites fossil (HKF-001) was collected from the tidal area at the seashore area of Nai Chung in 2009, no more specimens has been found again. Some human activities that cause damage to the rock on this site and becoming a public place of kitting & clam collecting. Otherwise, Some single, pair of specimens or small groups of poor preservation Hongkongites remains can be found in Fung Wong Wat area & seashore area of Pak Kok Chai sites of Tolo Channel Formation, and which is faulted at the rock base against the Devonian Bluff Head Formation (The most ancient formation in Hong Kong,), Hongkongites has not been recorded in Ma Shi Chau & Sham Chung.

REVIEWS OF THE STATUS OF GENUS HONGKONGITES

Hongkongites specimen shows that each coarse ribbing on both sides stops growing on the center of the abdomen to form a band with the same height as the shell surface (plain groove)
     Pg,  HKF-001A and cast model in right, bar length = 5mm,

Hongkongites and other relatives have combined to from a new genus Sulciferites by Arkell in 1975, and based on the specimens examined has coarse ribbing that is furcate near the umbilical shoulder and interrupted by VENTRAL groove [8], after that Hongkongites is widely described to be a synonym of Sulciferites (Donovan & Forsey, 1973), this classified standard had also been applied this genus with the new ‘Sulciferites hongkongensis Y. G. Wang et P. L. Smith, 1986 ‘ to related paper which was published in 1986.

No one has ever raised doubts for this taxonomical arrangement until 2020, after quite a lot of specimens has been collected and examined for a terms of more 10 years, we found that the has coarse ribbing that is furcate near the umbilical shoulder and teminated by PLAIN groove (Pg, HKF-001A,HKF-001C, HKF-020A), it indicated the genus Hongkongites is quite different from those characters of ‘Sulciferites’.

On the other side, two types of coarse ribbing can be observed from all specimens from the both origins (HK & GD), it may simply be divided as ‘straight ribbing (simple), I” and “forked ribbing (bifurcate), Y”, we noted that HK specimens demonstrates the irregular and random configuration of “I” & “Y” from their coarse rubbing between the whorl on the shell, and presents the IIIYIYIIYIYYI pattern, but 14 specimens from Huizhai, Jiexi County, Guangdong Province, China, which were identified as ‘Sulciferites hongkongensis Y. G. Wang et P. L. Smith, 1986‘ demonstrates the regular configuration of IYYYIYYYIYY pattern.

The genus Hongkongites should be restored and for all ‘Sulciferites’ specimens from Hong Kong.

After the fossils are hardened by Fe-rich minerals and weathered, sea eroded then mechanically rubbed, unclear relationships status between Hongkongites & its relatives may be caused by the most of specimens from the rock outcrops were in a poor state of preservation. Fortunately, an enigmatic NGF-001X specimen is found inside the rock materials when the Hongkongites rich stones were investigated. accompanying juvenile individuals with their partial well-preserved parents remains are completely preserved by the loose mudstone, the coarse ribbings of the adult ammonites are sharp, and they still have a bone-liked structure, which is obviously different from the matrix mudstone. HKF-020 provides very helpful evidences for the interpretation.

We are also examined the “smaller” specimens were found accompanying the “typical” Hongkongites, compact coarse ribbing on the shell with the IIIYIYIIYIYYI pattern, the specimen is also a specimen of Hongkongites and similar to the Hongkongites angulatoides (Quenstedt), Williams, 1943 (nomen nudum, no more information for further reference), we ever formally combined both to the same species, and smaller individuals as juvenile ammonite (Ng et al, 2009). After investigating for these specimens, a new species is described based on its unique morphic characters.

CLASSIFICATION & MORPHOLOGY

     Phylum: Mollusca
     Class: Cephalopoda
     Subclass: Ammonoidea(Extinct)
     Order: Ammonitida
     Suborder: Ammonitina
     Superfamily: Psilocerataceae
     Family: Schlotheimiidae
     Genus: Hongkongites

Era: Sinemurian (Early Jurassic strata, it spans the time between 196.5 Ma to 189.6 Ma)

Locality: Tolo Channel Foramtion, mainly Northern New Terrorities, Hong Kong. at Nai Chung & Sham Chum Area, in contrast to the strata of the adjoining crop of granite that cause damage to the fossil on this site by high temperature during the geological movement.  

 
Hongkongites hongkongensis (Grabau), 1923: A. HKF-001, Nai Chung, 2009, B. HKF-001A, C. HKF-001B, inner wall,  D. HKF-001B (Juvenile),  E. HKF-001C, F.HKF-001E
G. HKF-001F, shell fragment, H. HKF-001Z

1. 香港菊石 Hongkongites hongkongensis (Grabau), 1923 ( = Hoplites hongkongensis Grabau, 1920),  A Lower Cretaceous ammonite from Hong Kong, South China. Bull. Geol. Surv. China 5:  P.199–208.

Voucher Specimens: HKF-001, HKF-001A, HKF-001B,  HKF-001C, HKF-001D, HKF-001E, HKF-001F, HKF-001Z

Description: Shell diameter ca.20mm [ref. HKF-001=20mm, collected from Nai Chung in 2009, poor preservation, pebbled-liked fossil, no outer coiled shell, (HKF-001B,E) = 13mm, HKF-001Z=29mm], reddish to dark brown color, ventral narrowly round to oval, mid-evolute whorl with 3 coiled shell, slightly convex to flank flat, ribs sharp, simple and bifurcate, demonstrates the irregular configuration of IIIYIYIIYIYYI pattern. primitive coil contains 8~10 ribs, secondary coil contains 15~18 ribs and outer coil contains 20~25 ribs, 0.8~1.2mm in width, distance between ribs: 0.95~18mm (adult, outer ribs), coarse ribbing that is furcate near the umbilical shoulder and interrupted by plain groove. Ribbing on inner side of the shell (septum) strength varying considerably, simple and bifurcate, 0.9mm width, distance 1.0~1.9mm (ref. HKF-001B).

 
Hongkongites liberalis Ng et al., 2020, sp. nov, Adult.: A. HKF-020, slab,  B. HKF-020,countslab, C. HKF-020F, impression,  
D. HKF-020A, slab,  E. HKF-020A, counterslab, F. HKF-020B

Hongkongites liberalis Ng et al., 2020, sp. nov., Juvenile: A. HKF-020K, slab,  B. HKF-020, C. HKF-020, new-born, individual

2. 光復香港菊石 Hongkongites liberalis Ng et al., 2020, sp. nov., Etymology: this tiny species is named after the Roman goddess Libertas and refer to the compact radial pattern on the shell, such as sun rays, is a metaphor for bright freedom, we hereby record Hong Kong's glory in tribulation and the best wish for the future.
Typrus: HKF-020, Isotyprus: HKF-020A, HKF-020B, HKF-020C, HKF-020D,  HKF-020F, HKF-020E, HKF-020H, HKF-020I, HKF-020J,HKF-020K
Locality & yerars of collecting: Tolo Channel Formation, 2009~2020.
Fossil condition: impression and poor-preservation specimen form outcrop, well-preservation specimens from inside of the mudstone. 
Description:
Adult, a tiny and compact ammonid , coarse rubbings are more denser than Hongkongites hongkongensis (Grabau), 1923,  Shell diameter ca.15mm [(HKF-020B)=15mm、(HKF-020A)=15mm], , primitive coil contains 8~12 ribs, secondary coil contains 19~25 ribs and outer coil contains 30~35 ribs, sometimes it may confuse with the juvenile individuals of H. hongkongensis because they shared the same strata. Unlike those of H. hongkongensis, only impression or mold are collected, no cast can be observed in outcrop, all cast specimens of the new species are collected from the inside part of the fossil base accidentally.

Juvenile (HKF020, HKF-020A, HKF-020K): when the enigmatic HKF-020 specimen is examined under high power microscopy, we note that a special ‘Ombilic’ is a single individual, it is not fragments of umbilicus from the adult, it may be new born ammonid, which is clearly show that it is the specimen of existence of the parents & juvenile and this may be the first time it was discovered.

SUTURE LINES

12 3

45
Fig;1. HKF-001E H.hongkonensis, 2. HKF-020 H.liberalis (Adult), 3.HKF-020 H.liberalis (juvenile),  4.. scuture line, 5. Conceived reconstruction of suture pattern

The order and suborder of Ammonite are also the basis for identifying the age of life. The existing ammonite sutures are divided into four categories, representing species of different ages. Due to the poor preservation of Hongkongites, it is impossible to obtain directly from the specimens. Most of fossils have a rough shell surface, and most of them are attached to mudstone with a very thin brittle fossil layer, which is never feasible by sanding treatment. HKF-001E is a half-buried in the mud of adult Hongkongites, the keeping quality significantly better than the other specimens. Studying on the natural peeling of the outer surface of the shell part ( I ) leaves a light-colored impression or the outer edge of the hole (II)  has a regular ventral saddle and ventral lobe, HKF-020 is an uncompleted specimen that the shape of the suture near the umbilicus (III) could also be described.

Suture patterns of Hongkongites belongs to Ammonitic suture, it can be traced back to the Permian to Cretaceous.

NOTES

 A considerable amount of Hongkongites still exists in their sites of locality, and it is still possible to be found more perfect specimens in future. We don’t want any more foreign organizations to exhaust Hong Kong ’s fossils and take them away from Hong Kong. It should be understood that the importance of protection of both of fossils and geological sites, At the same time, defending our dignity, and our core values and especially for our young generation in Hong Kong is more important! This research project for this paper does not require any funding. We are very grateful for the beautiful and lovely Nature of Hong Kong.

REFERENCE:

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[2]《香港地質考察指引》香港土木拓展署, 2007/06
[3]  R.J.Swell et al., The Pre-Quarternary Grologgy of Hong Kong, GEO,GEDD, 2000/08.
[4]  蘇偉賢(Roderick J Sewell)等《香港地質-四億年的旅程 = Hong Kong Geology- A 400-million year journey》, HKGS, CEDD, 2009/09.
[5]  駱永明 等《香港地區土壞及其環境》, 科學出版社, 2007/09.
[6]  歐達敦著、李作明譯《香港岩石》, 市政局出版, 1988
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[8]  Sinemurian (Early Jurassic) ammonite fauna from the Guangdong region of southern China, Sinemurian (Early Jurassic) ammonite fauna from the Guangdong region of southern China, Sept., 1986. Journal of Paleontology 60(05):1075-1085.