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A case of symmetrical conjoined twins in a bottlenose dolphin Tursiops truncatuo

  • 1. Erasmus University Rotterdam and 2. Natural History Museum Rotterdam


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Erwin J.O. Kompanje
Naturalis (Nationaal Natuurhistorisch Museum), Leiden & Natuurhistorisch Museum Rotterdam
Kompanje, E.J.O., 2005 - A case of symmetrical conjoined twins in a bottlenose dolphin Tursiops
truncatus (Mammalia, Cetacea) - DEINSEA 11: 147-150 [ISSN 0923-9308]. Published 29 December
Case reports of conjoined twins (‘Siamese twins’) in wild mammals are very scarce. Most published
reports of conjoined twinning concern cases in man or in domestic mammals. In this article a case of
conjoined twinning in a wild mammal is described: a parapagus dicephalus with unilateral schistopro-
sopus in a bottlenose dolphin Tursiops truncatus stranded on the coast of the Netherlands in 1917. This
case concerns the oldest known case of a symmetrical conjoined twin in a cetacean species.
Correspondence: dr Erwin J.O. Kompanje, Natuurhistorisch Museum Rotterdam, P.O. Box 23452,
3001 KL Rotterdam, The Netherlands, e-mail:
Keywords: conjoined twins, parapagus dicephalus, double monster, Tursiops truncatus.
Conjoined twins (‘Siamese twins’) are well
known in man, in domestic and laboratory
mammals, domestic and wild birds and in
wild and captive-bred reptiles, amphibians and
fishes, but are very rarely described in wild
mammals. The precise incidence is unknown,
most likely due to high prenatal and antenatal
mortality. Almost all known cases of con-
joined twins in wild mammals concern unborn
embryos and fetus found during dissection of
the pregnant dead female. The aim of this arti-
cle is to describe a postnatal case of symmetri-
cal conjoined twins in a wild mammal.
Case report
A dead, 125 cm long, newborn female
dicephalic bottlenose dolphin Tursiops trun-
catus (Montagu, 1824), with open umbilicus,
was found on the beach at Wijk aan Zee, the
Netherlands, on 20 July 1917. The specimen
was sold to the Rijksmuseum voor Natuurlijke
Historie (now: Naturalis, National Museum of
Natural History) in Leiden. After preservation,
three photographs were made of the monstrum
(Fig. 1). Shortly afterwards, the specimen
was given on loan to the Anatomical Cabinet
of Leiden University for further study, but
nothing was published on this case. The speci-
men is untraceable now. It is neither in the
Anatomical Cabinet nor in any other museum,
and it is - unfortunately - most probably lost
for science. It supposedly got lost after an
English air raid during the Second World War
(Kompanje 2001). The three photographs
(reproduced here in Figure 1), still present
in the archives of the National Museum of
Natural History, form the only proof of this
rare case. This case was mentioned in a review
of Tursiops strandings along the Dutch coast
(Kompanje 2001).
A case of symmetrical conjoined twins in
a bottlenose dolphin Tursiops truncatus
(Mammalia, Cetacea)
 DEINSEA11,2005
Figure1ParapagusdicephalusinabottlenosedolphinTursiops truncatesfromWijkaanZee,theNetherlands,20July1917.
Conjoined twins are always conjoined in one
of only eight sites (Spencer 2001, 2003) and
are named after the site of union [see also
Kompanje (2005) - this volume - for further
details]. Normal twinning is very rare in
cetaceans. González et al. (1999) estimated
a 0.5% occurrence of multiple gestation of
all observed pregnant females in small ceta-
ceans. With the exception of the present case,
and of the case described by Cesarini et al.
(2004), only four cases of conjoined twins in
Cetaceans could be traced in the literature, all
found in unborn foetusses during dissections
in the Japanese and Russian whaling industry
(Table 1). Other complex foetal anomalies
found during these dissections includes holo-
prosencephaly, schistoprosopus and anoto-
cephaly, all in baleen whales (e.g., Zinchenko
& Ivashin 1960).
The present case is the first example of
conjoined twins in a wild newborn dolphin.
A diagnosis of a parapagus dicephalus mono-
somos dibrachius with unilateral schistopro-
sopus on the left head in a full-term female
newborn bottlenose dolphin seems accurate.
A second case in a wild newborn bottlenose
dolphin is described by Cesarini et al. (2004).
Judging from the description these authors
gave (two faces, one braincase, one foramen
magnum) this pair of conjoined twins should
be diagnosed as parapagus diprosopus.
Symmetrical conjoined twins in wild terres-
trial mammals have been very rarely reported
(Table 2). Spontaneous occurrence of con-
joined twins in laboratory animals is uncom-
mon. Szabo (1989) reported one conjoined
twin out of 10.000 in the rat and one case in
4000 rabbits bred in 20 years.
Spencer (2000a, 2000b, 2003) provides con-
vincing evidence that symmetrical conjoined
twins are the result of secondary fusion of two
originally separate monovular embryonic discs,
and are not the result of incomplete fission
producing a partially separated zygote.
Reference species taxonomy age
Kawamura 1969 Balaenoptera borealis thoracopagus fetus
Kawamura & Kashita 1971 Stenella coeruleoalba cephalopagus fetus
Kamiya et al. 1981 Stenella coeruleoalba parapagus dicephalus fetus
Zinchenko & Ivashin 1987 Balaenoptera acutorostrata thoracopagus fetus
Kompanje 2001 Tursiops truncatus parapagus dicephalus newborn
Cesarini et al. 2004 Tursiops truncatus parapagus diprosopus newborn
Reference species taxonomy age
Reisel 1671 Lepus europaeus cephalopagus newborn
Jung 1671 Lepus europaeus cephalopagus newborn
Seger 1671 Lepus europaeus cephalopagus newborn
Mentzel 1686 Alces alces cephalopagus fetus
Neugebauer 1851 Lepus europaeus cephalopagus newborn
Benesch 1957 Lepus europaeus cephalopagus newborn
Fay 1960 Odocoileus virginianus parapagus dicephalus fetus
 DEINSEA11,2005
Benesch, F.,1957 - Lehrbuch der tierärztlichen Geburts-
hilfe und Gynäkologie - Urban und Schwarzenberg,
München, Germany
Cesarini, C., I. Clémenceau, F. Dhemain, T. Jauniaux, O.
Van Canneyt, V. Ridoux, 2004 - Double faced monster
in the bottlenosed dolphin (Tursiops truncatus) found
in the Mediterranean sea - Veterinary Record 154:
Daniel, M.J.& M. Kershaw, 1964 - Recent congenital
anomalies in red deer in New Zealand - Journal of
Mammalogy 45: 480-483
Faust, I., 1999 - Zoologische Einblattdrucke und
Flugschriften vor 1800. Band II Vögel, Säugetiere -
Stuttgart, Hiersemann, Germany
Faust, I., 2001 - Zoologische Einblattdrucke und
Flugschriften vor 1800. Band III Paarhufer - Stuttgart,
Hiersemann, Germany
Fay, L.D., 1960 - A two-headed white-tailed deer fetus
- Journal of Mammalogy 41: 411-412
González, A.F., A. López & P. Benavente, 1999 - A
multiple gestation in a Delphinus delphis stranded on
the north-western Spanish coast - Journal of the
Marine Biological Association of the United Kingdom
79: 1147-1148
Jung, G.S., 1671 - Monstrum Leporinum - Miscellanea
Curiosa sive Ephemeridum Medico-Physicarum
Germanicarum Naturae Curiosorum. Annus Secundus:
Kamiya, T., N. Miyazaki & S. Shiraga, 1981 - First case
of dicephaly in Odontoceti - Scientific Reports
Whales Research Institute 33: 127-129
Kawamura, S., 1969 - Siamese twins in the sei whale
Balaenoptera borealis Lesson - Nature 221: 490-491
Kawamura, A. & K. Kashita, 1971 - A rare double mon
ster of dolphin Stenella caeruleoalba - Scientific
Reports Whales Research Institute 23: 139-140
Kompanje, E.J.O., 2001 - Review of strandings and
catches of Tursiops truncatus (Mammalia: Cetacea,
Odontoceti) in the Netherlands between 1754 and
2000 - Deinsea 8: 169-224
Kompanje, E.J.O., 2005 - Two cases of asymmetrical
conjoined twins in wild mammals from the
Netherlands - Deinsea 11: 139-145 (this volume)
Neugebauer, L., 1851 - Duplicität des Grössten theils des
Körpers beobachtet bei einem jungen Hasen (Lepus
timidus). Nova Acta Leopoldina 24: 17-48
Mentzel, C., 1686 - Alces monstroso partu & gratitudine
in hominis - Miscellanea Curiosa sive Ephemeridum
Medico-Physicarum Germanicarum Naturae
Curiosorum. Decuriae II, Annus Quintus: 6-8
Reisel, S., 1671 - Lepus Monstrosus - Miscellanea
Curiosa sive Ephemeridum Medico-Physicarum
Germanicarum Naturae Curiosorum. Annus Secundus:
Seger, G., 1671 - Vitulus Biceps - Miscellanea Curiosa
sive Ephemeridum Medico-Physicarum Germani-
carum Naturae Curiosorum. Annus Secundus: 168
Spencer, R., 2000a - Theoretical and analytical embryol-
ogy of conjoined twins: Part I: embryogenesis -
Clinical Anatomy 13: 36-53
Spencer, R., 2000b -Theoretical and analytical embryol-
ogy of conjoined twins: Part II: adjustments to union
- Clinical Anatomy 13: 97-120
Spencer, R., 2001 - Parasitic conjoined twins: external,
internal (fetuses in fetu and teratomas), and detached
(acardiacs) - Clinical Anatomy 14: 428-444
Spencer R., 2003 - Conjoined twins. Developmental
malformations and clinical implications - John
Hopkins University Press, Baltimore & London, VS
Szabo, K.T., 1989 - Congenital malformations in labora-
tory and farm animals - Academic Press Inc., San
Diego, VS
Zinchenko, V.L. & M.V. Ivashin, 1987 - Siamese twins
of minke whales of the southern hemisphere -
Scientific Reports of Whales Research Institute 38:
P.O.Box 23452, NL-3001 KL Rotterdam The Netherlands
... Including the present case in Phocoena phocoena, only ten cases of symmetrical conjoined twins in cetacean species have been described in the literature (Kawamura 1969;Kawamura & Kashita 1971;Zemsky & Budylenko 1973;Kamiya et al. 1981;Zinchenko & Ivashin 1987;Kompanje 2001Kompanje , 2005bDabin et al. 2004;Aytemiz et al. 2014;Tamburin et al. 2014 Conjoined twins can be separated in symmetrical and asymmetrical twins. Symmetrical conjoined twins concern two equal conjoined parts (the classic 'Siamese twins'). ...
... Some share one umbilical cord, other types, like the thoracopagus, have two umbilical cords. Stenella coeruleoalba cephalopagus fetuses Kamiya et al. 1981 Stenella coeruleoalba parapagus dicephalus fetuses Zinchenko & Ivashin 1987 Balaenoptera acutorostrata thoracopagus fetuses Kompanje 2001Kompanje & 2005b Tursiops truncatus parapagus dicephalus neonates Dabin et al. 2004 Tursiops truncatus parapagus diprosopus neonates Aytemiz et al. 2014 Tursiops truncatus parapagus dicephalus neonates Tamburin et al. 2014 Eschrichtius robustus thoracopagus neonates this contribution ...
... The symmetrical conjoined twin harbour porpoises described here can be determined as parapagus dicephalus. Three other cases of parapagus dicephalus are known in cetacean species, one in Stenella coeruleoalba (Kamiya et al. 1981) and two in Tursiops truncatus (Kompanje 2001(Kompanje , 2005bAytemiz et al. 2014). ...
Full-text available
The harbour porpoise (Phocoena phocoena) is the smallest and most abundant cetacean in NW European continental shelf waters. Their global abundance numbers at least ~700,000 individuals. Within the North Sea, total abundance has recently been estimated at approximately 345,000 animals. The species reproduces at a rate of one offspring every 1-2 years. In this article we describe a case of conjoined twins in the harbour porpoise: a parapagus dicephalus bycaught in the Southern North Sea in May 2017. Reports of conjoined twins in wild mammals are extremely scarce. This case concerns the second known case of twinning and the first case of conjoined twins in P. phocoena, the fourth known case of parapagus dicephalus in any cetacean species and the tenth known case of conjoined twinning in a cetacean species.
... Researchers found the aborted twins floating in a lagoon in Baja California, and the event was widely spread in scientific circuits as well as in social media (Lee, 2014;Murphy & Malm, 2014). Reports of conjoined or Siamese twins in wild mammals are very scarce; most reports are cases known in humans, in domestic animals or laboratory mammals (Kompanje, 2005). The precise incidence in wild mammals is unknown, most likely due to high prenatal and antenatal mortality. ...
... The precise incidence in wild mammals is unknown, most likely due to high prenatal and antenatal mortality. Almost all known cases of conjoined twins in wild mammals concern unborn embryos and fetus found during dissection of the dead pregnant female (Kompanje, 2005). Some cases of museum specimens of Siamese twins in terrestrial mammals do exist and are well known and documented, but none -to our knowledge -in the case of marine mammals 4 . ...
... Although usually associated with human populations (Mian et al. 2017), the occurrence of conjoined twins has been noted in creasingly in the animal world . Anomalies of this type occur extremely rarely in the animal world, but they have been observed in humans and in other mammals, including dolphins Tursiops truncatus (Kompanje 2005), leopard cats Prionailurus benga lensis (Kompanje & Hermans 2008), buffalo Bubalus bubalis bubalis (De La Ossa & Altahona 2010) and gorillas Gorilla gorilla (Langer et al. 2014), as well as in other groups of animals such as reptiles, including snapping turtles Chelydra serpentina (Cederstrom 1931) and crocodiles (Platt et al. 2012), as well as in fish (e.g. Von Bonde & Marchand 1929). ...
... In this study, twins of 2 major groups were found among whitefish: symmetrical, parapagus type (subtypes: diprosopus, dicephalic and dithoracic parapagus) and asymmetrical, where 1 of the twins is present as a parasitic form. The diprosopus parapagus subtype has also been observed in guppies (Moreno-Valcarcel et al. 2011, Petrescu-Mag et al. 2011) and tilapia Oreo chromis aureus (Shirak et al. 2013); the dicephalic parapagus subtype has been reported in dolphins (Kompanje 2005), turtles (Cederstrom 1931), tilapia (Owusu-Frimpong & Hargreaves 2000 and Atlantic salmon (Fjelldal et al. 2016); and the dithoracic parapagus subtype (types A and B combined) has been found in red tilapia (Huang et al. 1987), sea horse Hippocampus guttulatus (Blanco et al. 2012) and hybrid Atlantic salmon × Arctic char (Fjelldal et al. 2016). Studies conducted with human conjoined twins have confirmed that in most cases, such twins are formed in females (Mutchinick et al. 2011, Mian et al. 2017). ...
This paper describes for the first time various forms of conjoined twins in the common whitefish Coregonus maraena originating from the brackish waters of the Baltic Sea. The occurrence of conjoined twins was observed during the hatching of whitefish under controlled conditions. Two types of twins were identified: symmetric (parapagus) and asymmetric (parasitic form). The percentage of conjoined twins among the whitefish did not exceed 0.01% of the hatched larvae. The forms of twins observed in this study were similar to conjoined twins occurring among humans. One main type, parapagus, was identified in the group of symmetric twins with 3 subtypes: diprosopus parapagus, dicephalic parapagus and dithoracic parapagus. In its parasitic form, the parasitic twin occurred as a ‘cyclops’ or just as an eye growing out of the other twin’s head. We conclude that fish, as well as their fertilised eggs, can be used as a model system to observe how such twins are joined in humans because of the similarity with conjoined twins occurring in humans. Because of internal fertilisation in fish, as well as the size and transparency of egg cells in these animals, it is possible to observe the process of fertilisation, cell division and formation of an embryo and subsequently of twins, as a model for humans.
... Cases of conjoined twin cetaceans are very rare. The earliest report dates to 1917, when parapagus newborn female bottlenose dolphins (Tursiops truncatus) were reported in the Netherlands (Kompanje, 2005). Since then, 7 other pairs of conjoined twins have been reported in different Cetacean species: a thoracopagus fetal Balaenoptera borealis (Kawamura, 1969), one report of cephalopagus and one parapagus fetal Stenella coeruleoalba (Kawamura and Kashita, 1971;Kamiya et al., 1981), a thoracopagus fetal Balaenoptera acutorostrata (Patten, 1959;Zinchenko and Ivashin, 1987), one parapagus newborn Tursiops truncatus (Dabin et al., 2004), one thoracopagus case for the same species in Turkey (Aytemiz et al., 2014), and one case of ventropagus conjoined in Megaptera novaeangliae (Zemsky and Budylenko, 1970). ...
Full-text available
In January 2014, gray whale (Eschrichtius robustus) conjoined twin calves were found dead in Laguna Ojo de Liebre (Scammon’s Lagoon), Baja California Sur, Mexico. The thoracopagus (united ventrally at the chest) individuals were conjoined in the thorax region, sharing the navel and genital area, but with two distinct heads and flukes. Although observed in humans and domestic animals, this case is rare among cetaceans. Some conjoined twin cetacean fetuses have previously been reported; however, this is the first report of the congenital anomaly in Eschrichtius robustus.
... Furthermore Jonsgård (1953) reported a fin whale with six foetuses of varying sizes. Multiple foetuses are less frequent in Odontocetes than in Mysticetes (Lockyer, 1984), although they have been reported in sperm whales (Physeter macrocephalus) (Matsuura, 1940;Ohsumi, 1965;Gambell, 1972;Best et al., 1984;Clarke et al., 2011), short finned pilot whale (Globicephala macrorhynchus) (Escorza et al., 1994), striped dolphin (Stenella coeruleoalba) (Tobayama et al., 1970), bottlenose dolphin (Tursiops truncatus) (conjoined twins; Dabin et al., 2004;Kompanje, 2005;Aytemiz et al., 2014, and non-conjoined twins;Gray & Conklin, 1974;Lacave, 1991), Risso's dolphin (Grampus griseus) (Gassner & Rogan, 1997), beluga whale (Delphinapterus leucas) (Osborn et al., 2012), short-beaked common dolphin (Delphinus delphis) (González et al., 1999), Dall's porpoise (Phocoenoides dalli) (Nakamatsu, 2001) and harbour porpoise (IJsseldijk et al., 2014). Of these cases, the striped dolphin, sperm whale, common dolphin, Risso's dolphin, Dall's porpoise, harbour porpoise and conjoined twins of the bottlenose dolphins were free-living individuals that stranded dead, the others were all captive animals. ...
The present study is the first record of twinning in Lagenorhynchus acutus and indeed any Lagenorhynchus sp. Both foetuses were male and located in the left uterine horn, had distinct grossly normal placentas and amniotic sacs, and were therefore likely dizygotic twins. The twins were an incidental finding in an animal that died of a systemic Brucella ceti infection.
... Parapagus dicephalus is well documented by Aldrovandi in domesticated animals (Fig. 3.) and also in fish, bird and reptile species (Aldrovandi 1642, 416-430). The malformation is also well known and documented in recent times in both wild (Gould & Pyne n. d., 157;Dabin et al. 2004;Kompanje 2005b) and domestic animals (Hámori 1974, 345). An intresting aspect of symbolism of the two-headed animals is that in Šumma izbu the two heads mean some kind of a division, and are thus always recorded as a bad sign (Jastrow 1914, 14-15), while in Antiquity and in the Middle Ages the double-headed eagle became the symbol of unity in the iconography of many noble and royal families in Europe and Asia (Hohenlohe-Waldenburg 1871, 17). ...
Full-text available
Sources concerning various human congenital malformations are well known from early Antiquity to the Modern Times, but what about the animals? The first known source is the Šumma izbu, an ancient Mesopotamian compendium of around 2,000 teratological omens from 1300 BC. In these texts first descriptions of many disorders can be found such as different types of conjoined twinning or polydactyly. Some of these omens appear in the Roman Period by Julius Obsequens, Valerius Maximus and Tacitus. The thesis, that the Babylonian- Assyrian point of view spread through Asia Minor to the Greeks, and Romans originates from Morris Jastrow jr. (1914). The Latin term monstrum reflects the idea, that such phenomena sign some upcoming event to demonstrate the will of a deity. We have many more written and pictorial sources from the late Middle Ages from Ambroise Paré, Thomas Bartholinus and Ulisse Aldrovandi. The scarcity of comparable archaeological materials can be answered with four reasons: 1. Minor anomalies on the bones are hard to detect in the animal. 2. Many major abnormalities resulted in the animal's perinatal death. In this stage of development the bones are poorly mineralized, resulting a rapid dissolution. 3. Many inherited deformities affected the soft tissue, nearly always missing from archaeological materials. 4. Malformed stillborns were often fed to the dogs or thrown into rivers.
Full-text available
On 4 August 2014, a male conjoined dicephalic bottlenose dolphin (Tursiops truncatus) calf was found dead on the beach of Dikili/İzmir, the Aegean coast of Turkey. This is the first case of conjoined cetacean reported in Turkey and the second in the Mediterranean Sea.
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This study presents the second worldwide report on abnormal embryos of the sharpnose sharks, Rhizoprionodon, based on the two species (Rhizoprionodon porosus and Rhizoprionodon lalandii) occurring on the Brazilian coast. For R. porosus two conjoined twin embryos showing complete duplication of the vertebral column, viscera and several external structures (head, first and second dorsal fins, pectoral fins), and scoliosis in both axis at the pelvic fin level are reported. The three embryos of R. lalandii exhibited numerous lordosis and kyphosis along the entire vertebral column. The possible relationship between anomalies and the human major threats to sharks is discussed based on previous reproductive, genetic and ecotoxicological studies on R. lalandii for southern Brazil.
Full-text available
The present study is the first record of twinning in Delphinusdelphis. The first foetus was a female of 72 cm total length which had a curved caudal area. This animal was located in the left uterine horn, very close to the genital aperture. The second foetus was a male of 46 cm total length and its external morphology was deformed. It was located in the uterus and the nose was shorter than the female foetus. Documented incidences of twinning in cetaceans are rare.
ALTHOUGH there have been comprehensive biological studies of whales since 1925 when the Discovery Committee founded the research station at South Georgia, there have been no reports of Siamese twins in whales as far as I know. I now report briefly the results of morphological observations on sei whale Siamese twins found on the Japanese whaling factory ship Nisshin Maru (Taiyo Fisheries Co.) in the Antarctic whaling season 1967–68.
A review of over 1,800 publications concerning the embryology and pathologic anatomy of conjoined twins provides convincing evidence that they all result from the secondary union of two originally separate monovular embryonic discs. This “fusion” theory seems to be confirmed by the adjustments to union and the pattern and incidence of specific anomalies at the proposed sites of conjunction in more than 1,200 cases, all of which can be arranged in two uninterrupted series of cases, the one united dorsally (in the neural tube) and the other, ventrally (over a shared a yolk sac). No theoretical “fission” of the vertebrate embryo at any stage of development, in any plane, in any direction can explain (1) the selection of the observed sites of fusion, (2) the details of the union, or (3) the limitation to the specific areas in which the twins are found to be joined. Part I of this disquisition deals with the pertinent normal and theoretical embryology, the adjustments to union, and the parasitic cases, as well as conjoined triplets and quadruplets, and a comparison of oviparous and viviparous embryos. Part II (in a subsequent issue of this journal) will compare and correlate the abnormalities of the various organ systems involved in 1,200 cases. Clin. Anat. 13:36–53, 2000. © 2000 Wiley-Liss, Inc.
A previous report in this journal (Spencer, 2000) discussed the probable embryologic etiology of conjoined twins, along with a system of classification based on the embryological structures postulated to be involved in the union. Part II correlates and compares the variations in the abnormal development of the individual organ systems in more than 1,200 actual cases, revealing details of embryogenesis not considered in previous publications. The site, incidence, and range of anomalies in the conjoined structures, as well as the associated malformations, follow a definite pattern as the union proceeds from one area to another; many can be explained in relation to the proposed embryologic adjustments to union, including both temporal and spatial influences. In addition, six currently inexplicable or unclassifiable cases are briefly described (including one with 12 feet), as well as two examples of early abnormal conjoined twins. Clin. Anat. 13:97–120, 2000. © 2000 Wiley-Liss, Inc.
During the course of researching the embryologic etiology of conjoined twins, more than 1260 individual cases were collected from the literature and the reported abnormal anatomy tabulated and evaluated in the light of known embryology. It soon became apparent that the association of conjoined twins and their parasites with fetuses in fetu, acardiacs, and teratomas was more frequent than could be attributed to chance. These anomalous fetuses form a continuum, strongly suggesting that they are all variations of abnormal conjoined twinning, with the site of union and the extent of damage (or defect) of one embryo resulting in (1) an externally attached parasitic twin, (2) an enclosed fetus in fetu, (3) an internal teratoma, or (4) an acardiac connected via the placenta. Common patterns among them are a family history of twinning, the predominance of females, and the frequent presence of a twin or triplet accompanying the malformation. The several reports of chromosomal abnormality suggest that perhaps, at least on occasion, it is a genetically imperfect embryo that develops into a defective fetus. Of singular importance is the fact that rarely, if ever, is either a functional heart or a competent brain found in any of these abnormal fetuses, suggesting that the etiology of all of them is a primary cardiac malformation with secondary disruption in the development of the brain.
1957 -Lehrbuch der tierärztlichen Geburtshilfe und Gynäkologie -Urban und Schwarzenberg
  • F Benesch
Benesch, F.,1957 -Lehrbuch der tierärztlichen Geburtshilfe und Gynäkologie -Urban und Schwarzenberg, München, Germany