106,970 research outputs found
Hybrid automata dicretising agents for formal modelling of robots
No full textSome of the fundamental capabilities required by autonomous vehicles and systems for their intelligent decision making are: modelling of the environment and forming data abstractions for symbolic, logic based reasoning. The paper formulates a discrete agent framework that abstracts and controls a hybrid system that is a composition of hybrid automata modelled continuous individual processes. Theoretical foundations are laid down for a class of general model composition agents (MCAs) with an advanced subclass of rational physical agents (RPAs). We define MCAs as the most basic structures for the description of complex autonomous robotic systems. The RPA’s have logic based decision making that is obtained by an extension of the hybrid systems concepts using a set of abstractions. The theory presented helps the creation of robots with reliable performance and safe operation in their environment. The paper emphasizes the abstraction aspects of the overall hybrid system that emerges from parallel composition of sets of RPAs and MCAs
Freedom, necessity, and the knowledge of God in conversation with Karl Barth and Thomas F. Torrance
No full text"Paul D. Molnar discusses issues related to the concepts of freedom and necessity in trinitarian doctrine. He considers the implications of "non-conceptual knowledge of God" by comparing the approaches of Karl Rahner and T. F. Torrance. He also reconsiders T. F. Torrance’s "new" natural theology and illustrates why Christology must be central when discussing liberation theology. Further, he explores Catholic and Protestant relations by comparing the views of Elizabeth Johnson, Walter Kasper and Karl Barth, as well as relations among Christians, Jews and Muslims by considering whether it is appropriate to claim that all three religions should be understood to be united under the concept of monotheism. Finally, he probes the controversial issues of how to name God in a way that underscores the full equality of women and men and how to understand "universalism" by placing Torrance and David Bentley Hart into conversation on that subject.
T. Molnar, Dieu et la connaissance du réel. Coll. « Philosophie aujourd'hui ». — P.U.F., Paris, 1976
No full textCollange Jean-François. T. Molnar, Dieu et la connaissance du réel. Coll. « Philosophie aujourd'hui ». — P.U.F., Paris, 1976. In: Revue d'histoire et de philosophie religieuses, 58e année n°2,1978. pp. 243-244
T. Molnar, L'Utopie. Eternelle hérésie, Paris, Beauchesne, 1973 / Lyon, Les Utopies et le Royaume, Paris, Le Centurion, 1973
No full textCollange Jean-François. T. Molnar, L'Utopie. Eternelle hérésie, Paris, Beauchesne, 1973 / Lyon, Les Utopies et le Royaume, Paris, Le Centurion, 1973. In: Revue d'histoire et de philosophie religieuses, 54e année n°4,1974. p. 580
Albertosaurus cf. A. lancensis Molnar 1980
No full textGeneral.— This specimen attributed to Albertosaurus cf. A. lancensis (LACM 23845) is represented only by limb material and fragments of the skull and jaws. This description will emphasize the postcranial elements, with sufficient attention to the cranial remains to demonstrate that the specimen is not referable to Tyrannosaurus. The prefrontal, not elsewhere described or well illustrated in the literature, will also be treated in detail. In view of the incompleteness of the material here described, and of the descriptions of albertosaur postcranial material by Lambe (1917) and Parks (1928) and of tyrannosaur postcranial material by Osborn (1906, 1916), this description will focus on differences of LACM 23845 from described forms. Detailed comparison, not possible with the other tyrannosaurids, was made with the disarticulated Tyrannosaurus rex skull (LACM 23844) collected from the adjacent quarry. Nasal. — The nasals of LACM 23845 differ from those of T. rex (AMNH 5027, LACM 23844) in showing fewer and lower dorsal rugosities, and having an abrupt flexure in the sagittal plane. The nasals of Albertosaurus libratus, Daspletosaurus torosus and T. rex are straight or slightly convex: a similar flexure, however, is present in at least one specimen of Tarbosaurus bataar (PIN 551-3, Maleyev, 1974, Tab. II, fig. 1). The posteriormost portion of the nasals of LACM 23845 is lacking, but they appear to have narrowed posteriorly less markedly than those of T. rex (Osborn, 1912, Pl. 1), and more than in A. libratus (Russell, 1970, fig. 2). The nasal contact of the frontals was W-shaped and broader relative to the width of the frontals than in T. rex. Maxilla.— The maxillae were minced prior to collection. The largest piece includes the anteroventral margin of the antorbital fossa and shows that it bounded the anteriormost antorbital fenestra as in both Albertosaurus and Tyrannosaurus. Lachrymal.— The horizontal ramus of the right lachrymal is preserved, showing the lachrymal ‘horn’ found in A. libratus was not present in this form. The lachrymals of the type specimen of A. lancensis are incomplete, the left poorly preserved, and the right apparently reconstructed in plaster, thus detailed comparison could not be made. In T. rex the horizontal ramus of the lachrymal is deeper dorsoventrally and the medial and lateral surfaces more nearly parallel than in this specimen (where they converge anteriorly). Additionally, the articular surface for the nasal is restricted to the lower half of the medial face of the lachrymal in LACM 23845, while in T. rex (LACM 23844) this surface occupies threequarters of the height of that face. Prefrontal (Text-fig. 1).— Both prefrontals are nearly complete. This specimen is the only one known to me in which the prefrontals have been freed from articulation with the other elements, and can thus be described in detail. The prefrontal is roughly tetrahedral in shape with the slightly convex base dorsally. The anterior face is smoothly concave on the left, and concave with a low ridge on the right prefrontal. The medial face smoothly curves into the posterior, and both are slightly convex: the anterior face only is clearly distinct from the others. The posterior and medial faces both articulate with the frontal, while the anterior contacts the lachrymal. The lack of published descriptions of theropod prefrontals prevents any comparisons with other taxa. Frontal.— Both frontals are preserved: the right lacks only the postorbital articular surface, while of the left only the medial portion is present. The nasal contact is wider relative to the length of the frontals than in T. rex. In dorsal aspect the prefrontal contact is less angular than in T. rex, more like that of A. libratus. This contact is poorly preserved in the type specimen of A. lancensis. A partial braincase of Tyrannosaurus sp. (MMS 51-2004) from South Dakota shows a prefrontal articular surface that is dorsoventrally elongate, concave and sutural (Text-fig. 2). That of LACM 23845 is triangular and smoothly concave. While some movement at this contact may have been allowed in the latter form, this was not the case in T. rex. Parietal.— The anteromedial portions of the parietal are preserved, and are indistinguishable from those of Albertosaurus and Tyrannosaurus. Supraoccipital.— The medial portion of the supraoccipital crest and adjoining portion of the sagittal crest are present. The dorsal margin of the sagittal crest reaches to the flattened dorsal margin of the supraoccipital crest posteriorly. In T. rex the dorsal margin of the sagittal crest does not extend so far dorsally, while both A. lancensis and A. libratus agree with LACM 23845. The right supraoccipital ala is thicker along its dorsal margin than the left. Interestingly, the supraoccipital crest of A. libratus (AMNH 5336), also shows such an asymmetry (not found in T. rex), but reversed, that is, with the thicker ala on the left. The supraoccipital alae of LACM 23845 are thicker than in the type specimen of A. lancensis. Pterygoid.— Most of the quadrate processes of both pterygoids are present. They are thicker than usual for the quadrate of T. rex (although one specimen, CM 1400, matches them in thickness). Quadratojugal.— Most of this element is preserved, represented by complementary pieces from right and left. In general form it agrees with those of other tyrannosaurids: those of the type specimen of A. lancensis are too incomplete for comparison. The upper quadrate articular surface of this element is polygonal in outline and sutural in T. rex (LACM 23845), and elliptical and smooth in Albertosaurus cf. A. lancensis. The anterior portion of that articular surface in T. rex (LACM 23844) is a marked concavity, while that of LACM 23845 lacks any concavity. The lower quadrate articular surfaces also differ, but both specimens are incomplete in this region and the extent of this difference is in doubt. No disarticulated quadratojugal of Albertosaurus could be located for comparison. Dentary, angular and prearticular. — The central portions of the right dentary and of both angulars and both prearticulars are preserved. These are indistinguishable from those of Albertosaurus and Tyrannosaurus except that the ventral margin of the posteroventral process of the dentary bears posteriorly a small, distinct medial shelf in T. rex (LACM 23844) absent in LACM 23845. Surangular.— Most of the right, but only fragments of the left surangular are preserved. The anterior dentary process lacks the internal, longitudinal bar found in T. rex (LACM 23844). Ulna (Text-fig. 3).— The left ulna lacks only the radial and olecranal edges of the proximal articular surface. Expanded at both ends, it has a slight taper distally in lateral view. The proximal articular surface is inclined at about 45° to the long axis of the ulna, and both it and the distal articular surface are subtriangular in shape. There is no sign of a pronounced olecranal process as in Albertosaurus and Daspletosaurus, the ulna most resembling that of juvenile Albertosaurus libratus (AMNH 5664). The shaft tapers less than in any other tyrannosaurid. As in Deinonychus antirrhopus (Ostrom, 1969) the margins of the joint capsule at the distal extremity are traceable as a distinct angulation of the surface: the radial surface has a slight rugose ridge distally, similar to that of D. antirrhopus suggested by Ostrom (1969) as the attachment of the distal radioulnar ligament. The ulna is 131 mm long, and 26 mm in distal diameter. Metacarpal (Text-fig. 3).— The metacarpal II is broader than deep. It is 70 mm long, 29 mm in maximal proximal diameter and 21 mm in maximal distal diameter. Manual ungual phalanx (Text-fig. 3).— The ungual lacks the tip and a portion of the basal proximal angle. It differs from those of A. libratus (and Tarbosaurus bataar) in that, although incomplete, it shows no sign of a proximal tendon tubercle, which thus must have been poorly developed at best. In lateral aspect the proximal articular surface of the manual claw of tyrannosaurids (and most theropods) is arcuate in the sagittal plane: in this specimen it is not arcuate, but consists of two nearly plane surfaces meeting at an oblique angle. Such an angled surface would have reduced the mobility of this claw on the adjacent phalanx. Femur (Text-fig. 4).— The proximal twothirds of the left femur is present. The lesser trochanter is broken away, and the shaft crushed so that reliable measurements of the diameter cannot be made. The femur, with long, straight shaft and marked, offset head, resembles those of other tyrannosaurids, but appears more slender than most. The proximal proportions match those of the femur of Dryptosaurus aquilunguis (Cope, 1871), but the shaft is less curved in the sagittal plane. The fourth trochanter is less prominent than in adult tyrannosaurids, but resembles that of juvenile A. libratus (AMNH 5664). It appears more proximally placed than in D. aquilunguis, but the incompleteness of the femora of both forms makes it difficult to be sure. Comparing the ratio of the width of the proximal end to the distance from that end to the distal termination of the fourth trochanter suggests that the trochanter in LACM 23845 is more proximally placed than in A. libratus or T. rex. Tibia (Text-fig. 5).— The proximal half of the left tibia is preserved. In proximal view it is roughly triangular in form and narrower than those of other albertosaurs, which are roughly quadrangular, except ‘Gorgosaurus' novojilovi (Maleyev, 1974). The cnemial and fibular crests are well-developed. The cnemial crest extends further laterally than in other albertosaurs, except‘G.’ novojilovi, projecting to a position anterior to the head of the fibula. This tibia, as preserved, most closely resembles those of Coelosaurus antiquus (Leidy, 1865, Pl. Ill, fig. 3) and ‘G3 novojilovi. The tibial condyles are prominent, the lateral condyle showing an anterior projection also seen in A. sarcophagus (Parks, 1928, fig. 13), but not in A. libratus (Lambe, 1917, fig. 43). Fibula (Text-fig. 6).— The right fibula is complete. In lateral view the proximal expansion is roughly symmetric about the midline, a condition found in D. aquilunguis but not in other tyrannosaurids. The fibula is more slender than those of T. rex (LACM 23844) and D. aquilunguis. The anterior margin is less convex in lateral view, and the dorsal margin more nearly flat than in T. rex, both character states being shared with A. sarcophagus and A. libratus. Astragalus.— The right astragalus has been described and figured by Welles and Long (1974). They have concluded that it resembles those of the albertosaurs and is quite distinct from that of T. rex (AMNH 5027). It should be noted however, that an incomplete astragalus collected with the remains of T. rex, LACM 23844, and attributed to that specimen (being of the appropriate size) does not resemble the astragalus attributed to AMNH 5027, but rather the albertosaur astragali. Welles and Long (1974) felt that the astragalus of Dryptosaurus aquilunguis, interpreted as worn, was the closest in form to that of LACM 23845. Metatarsus (Text-fig. 7).— The right metatarsal II and distal half of metatarsal III are present. They resemble those of A. libratus, with indication of the characteristic proximal narrowing of metatarsal III. The proximal face of metatarsal II bears a prominent expansion laterally, like those of T. rex and adult A. libratus, but absent in A. sarcophagus (Parks, 1928) and juvenile A. libratus (AMNH 5664). These metatarsals are less stout than those of T. rex, but stouter than those of‘G.’ novojilovi. Pedal phalanges (Text-fig. 7).— Eleven phalanges of the right pes are present, more or less complete. They are indistinguishable from those of albertosaurs, and only slightly more slender than those of T. rex (LACM 23844). COMPARISONS The form of the quadratojugal and of the metatarsus of LACM 23845 indicate that this specimen represents a tyrannosaurid. Comparison with Tyrannosaurus (AMNH 5027, LACM 23844 and MMS 51-2004) shows several cranial differences that appear significant: width of the posterior portion of the nasals; lachrymal-nasal articulation; frontal-prefrontal articulation; quadratojugal-quadrate articulation; relation of sagittal and supraoccipital crests. Other differences (e.g. in nasal form) may well be individual anomalies or age dependent features. These differences are reinforced by differences of proportion of the limb elements and of the form of the fibula. The limb element proportions match those of Albertosaurus, as do some of the cranial features (e.g. form of the horizontal ramus of the lachrymal) in which LACM 23845 differs from T. rex. Rozhdestvenskii (1965) found that in Tarbosaurus bataar postcranial material of immature specimens was more slender than that representing adult specimens, while Russell (1970) found a very similar situation for Albertosaurus libratus. Rozhdestvenskii had also suggested that Albertosaurus lancensis might be an immature Tyrannosaurus rex, a suggestion with which Russell disagreed, pointing out that the type specimen of A. lancensis showed tightly interlocking cranial sutures and well developed supraoccipital alae, both of which indicated adulthood. Because LACM 23845 does not show tightly interlocking cranial sutures and does show more slender proportions than Tyrannosaurus the reasons for not regarding it as an immature Tyrannosaurus must be clearly stated. These are three: first, the supraoccipital alae are well-developed; second, the marked difference in the form of the prefrontal-frontal and the quadratojugal-quadrate articulations from those of Tyrannosaurus', and third, the difference in form of the proximal fibula from that of Tyrannosaurus. Because the length of the fibula of LACM 23845 is about 80% that of T. rex (LACM 23844) I regard it as unlikely that the form of the articulations or the proximal part of the fibula could change in the required amount during the remaining growth, were LACM 23845 an immature T. rex. Two Maestrichtian North American theropod taxa might accommodate this material, neither of them well known. These are Albertosaurus lancensis (Gilmore, 1946), represented by the type skull and jaws, and Dryptosaurus aquilunguis (Cope, 1866, 1871) represented largely by incomplete postcranial elements. The recent assertion that many of the Maestrichtian dinosaurs of New Jersey in fact pertain to genera known from the Rocky Mountains (Baird and Horner, 1977), emphasizes the possibility that LACM 23845 might belong to Dryptosaurus. There are some specific points of resemblance in the form of the astragalus and the manual claws, that of D. aquilunguis having a poorly developed basal tubercle as well as the closest approach to LACM 23845 in form of the proximal articular surface. Dryptosaurus is the only other form to have a ‘symmetrical’ proximal fibula, however the form and proportions of the rest of the fibula differ, and the ventral end is much more acute in Dryptosaurus than in LACM 23845. Although recognizing that incomplete material of several of the forms here considered makes comparison difficult, there seem to be more resemblances to Albertosaurus than to Dryptosaurus. Specifically LACM 23845 resembles Albertosaurus in: form and proportions of metatarsus; proportions of fibula; relation of sagittal to supraoccipital crest; form of horizontal ramus of lachrymal; form of distal fibula. LACM 23845 seems unique among tyrannosaurids in the subdued olecranal process of the ulna, the angulate proximal articulation of the manual claw, and the absence of a lachrymal ‘horn.’ Reference to A. lancensis is largely on stratigraphic grounds: the material is too incomplete to support reference to taxa not otherwise know from the Maestrichtian, such as A. libratus, A. sarcophagus or Daspletosaurus torosus.Published as part of Molnar, R. E., 1980, An albertosaur from the Hell Creek formation of Montana, pp. 102-108 in Journal of Paleontology 54 (1) on pages 102-107, DOI: 10.5281/zenodo.103972
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
gen_indet sp_indet Molnar 1978
No full textDuring the summer of 1966 Mr. Harley Garbani, of the Museum of Natural History, Los Angeles County, collected the snout and associated pieces of a theropod skull and jaws, catalogued as LACM 28471. These were from a dark grey clay of the Hell Creek Formation on the F. S. McKeever Ranch, S34 T 21N R37E, near Jordan in Garfield County, Montana (LACM Locality 7245). The material was found near a large YTriceratops skull, but the level in the Hell Creek Formation was not recorded. The specimen was initially identified as a juvenile Tyrannosaurus rex because of its small size and occurrence in the Hell Creek Formation. Thus the specimen is of considerable interest, for it represents an individual smaller than any known to pertain to the Tyrannosauridae. However, it appears likely to be neither Tyrannosaurus rex nor Albertosaurus lancensis (although possibly juvenile) and the existence of a third large theropod in the Hell Creek is itself of interest. Finally, it is one of the few theropods from which an endocranial mold has been prepared. Although the specimen is not referrable to any well known taxon, the incompleteness of the material renders it unwise to erect a new taxon for it at this time, and following Galton (1973) in a similar situation, it will herein be called the Jordan theropod. COLLECTION DESIGNATIONS AMNH — American Museum of Natural History (New York). LACM — Museum of Natural History, Los Angeles County (Los Angeles). MMS — Minnesota Museum of Science (St. Paul). NMC — National Museum of Natural Sci ences (Ottawa). PIN — Paleontological Institute of the Academy of Sciences of the USSR. (Moscow). USNM — United States National Museum (Washington). YPM — Peabody Museum of Natural History, Yale University (New Haven). DESCRIPTION Maxilla.— Both maxillae (Text-fig. 1) are preserved posteriorly to a line just behind the anterior margin of the antorbital recess. The term antorbital recess is used here and throughout to designate the excavation often surrounding the antorbital fenestra(e) in archosaurs. Similarly the term supratemporal recess will be used for the excavation sometimes surrounding the supratemporal fenestra. The anterodorsal and ventral margins of the maxilla converge anteriorly at an angle of 50 degrees, as compared to 80 in Tyrannosaurus and 70 (in immature specimens) to 90 in Albertosaurus. This, together with the shallow nasals, gives the preserved portion of the snout a more nearly triangular appearance than is usually found among Cretaceous theropods. Anteriorly there is a row of foramina 1 cm above the ventral margin. Little of the antorbital recess is preserved. Its anterodorsal margin slightly overhangs the lateral wall and a foramen extends anterodorsally from the anterior apex of the recess. This would correspond with the anteriormost antorbital fenestra of Russell (1970). It is clear that were a second (anterior) antorbital fenestra present, it did not extend to the anterior margin of the recess. Copyright © 1978, The Society of Economic \ Paleontologists and Mineralogists A shallow concavity in the anterodorsal margin of the left maxilla marks either the ventral margin of the naris or of the subnarial foramen (sensu Madsen, 1976A). This concavity is 3.5 cm long and terminates anteriorly 0.5 cm above the ventral margin. The medial surfaces of both maxillae have been obliterated, except for two medially directed shelves subparallel to the ventral margin. The anterior shelf is just ventral to the posterior termination of the previously described concavity 3 cm above the alveolar margin. This process is unbroken at its posterior termination as is the posterior shelf at its anterior termination. This suggests the existence of a channel between the two, possibly similar to the internal passage connecting to the subnarial foramen in Allosaurus (Madsen, 1976A). However, in Allosaurus this passage opens between the maxilla and premaxilla not within the maxilla. Both shelves (each 2 cm long as preserved) slope downwards anteriorly. They are presumably portions of the palatal process of the maxilla. The form of the maxilla reconstructed to correct for displacements at the breaks is given in Text-figure 2. Nasal.— Both nasals (Text-fig. 1) are preserved for a length of 16 cm posteriorly from the premaxillary junction. The maximum width, near the posterior end of the nares, is at least 3.4 cm. The nasals preserved in articulation are long, narrow, parallel-sided elements slightly flared at the maxillary processes. Strongly arched in the transverse plane, their maximum height is 1.4 cm. The premaxillary processes diverge anteriorly to receive between them the nasal processes of the premaxillae for a distance of 1 cm. The dorsal surface of the nasals is smooth: the median contact is preserved anteriorly but apparently obliterated by fusion beyond a break 5 cm from the premaxillary contact. The naso-maxillary suture is smooth as in dromaeosaurids and unlike the dentate appearance it assumes in tyrannosaurids. Frontal.— The right frontal (Text-fig. 3) lacks only the lateral portion (contacting the postorbital) while the left is less complete. The frontal is subtriangular in form when viewed dorsally, with the most acute angle directed anteriorly, an oblique angle directed posteromedially, and the third, truncated, directed posterolaterally. The fronto-parietal contact is V-shaped, with the apex directed anteriorly, and the sutures curving laterally until they are in the transverse plane. This contact is a serrate suture, and thus immobile, in contrast to that of Dromaeosaurus albertensis (Colbert and Russell, 1969). The posterolateral region of the right frontal shows a serrate sutural laterosphenoid contact surface. The postorbital contact, preserved on the left frontal, is a shallow, anteroposteriorly elongate concavity approaching to within 3 mm of the prefrontal contact. Since the surface here is worn it is not clear whether the postorbital came into contact with the prefrontal thus excluding the frontal from the orbital margin. Both prefrontal contact surfaces are preserved. They are deep, teardrop-shaped concavities, with the “tails” of the “teardrops” directed anterodorsally. Ventrally adjacent to the “tail” is a deep groove. The articular surface for the nasal, although worn, shows a medial trough presum- ably occupied by a tongue of the nasal. Lateral shelves were presumably also occupied by portions of the nasals which thus slightly overlapped the frontals at the junction, and gave the contact the shape of a W when viewed from above. Such a contact is also found among the tyrannosaurids (e.g. Albertosaurus, Daspletosaurus', Russell, 1970). The dorsal surface of the frontals is smooth rising posteriorly to the parietal junction. This rise extends 1.5 cm anteriorly from the contact along the midline to form a low sagittal crest. There is no indication of invasion of the frontals by a supratemporal recess, and although this portion of the surface is worn, the wear is so slight as to obscure none but the faintest indication of such a recess. Hence the frontals differ from those of many other theropods {Allosaurus, Dromaeosaurus, the saurornithoidids, the tyrannosaurids, etc.) in which the recesses unmistakably invade them. The ventral surface of the frontals is better preserved and from this a partial endocranial mold has been made. The cristae cranii, the longitudinal ridges bounding the endocranial cavity, are the most prominent features. Only the anterior portions of the cristae are preserved. They show no sign of union with a bony element ventrally in the region of the taenia medialis, unlike the case in Allosaurus (Madsen, 1976A), Saurornithoides (Barsbold, 1974), Tyrannosaurus (Osborn, 1912; Bellairs, 1949), and a specimen tentatively referred to Albertosaurus (LACM 23845). In the Jordan theropod the cristae seemingly contacted only epioptic membrane. The cristae are slightly curved, convex medially, giving a constriction of the olfactory passage as in the tyrannosaurids and Dromaeosaurus. Parietal.— Only the anteromedial portion (5 cm in length) of the parietals (Text-fig. 3) is preserved, fused along the midline. The maximum width as preserved is 4.2 cm, which since portions of both proötic contacts are present, must be close to the actual value. The proötic union was a serrate suture. The smooth dorsal surface rises medially to a sagittal ridge which, in turn, rises abruptly posteriorly suggesting a supraoccipital crest was present (but not preserved). The line of intersection between the ventral surface and the sagittal plane is smoothly concave ventrally, with only a small depression on the midline near the center of the portion preserved. Dentary.— Anterior portions of both dentaries (Text-fig. 1) are preserved with the symphysis in contact. The symphysis is 4 cm long, the preserved portion of the right dentary 15 cm long, and that of the left 14.5 cm long. Both are 4 cm deep and 1.8 cm wide at the posterior break. While resembling those of most theropods, these dentaries differ in two characters: 1) the ventral margin of the symphysis is less inclined in lateral aspect, 40 degrees to the horizontal, versus 50 degrees in mature tyrannosaurids (Albertosaurus, Daspletosaurus and Tyrannosaurus) and 2) the alveolar margin ascends anteriorly, then levels off at the region of the symphysis like that of Baurusuchus (Romer, 1956, Fig. 75D). Only Kelmayisaurus petrolicus (Dong, 1973) and the immature Albertosaurus libratus (AMNH 5664) show a comparably low angle to the symphysis. Spinosaurus (Stromer, 1915) and Marshosaurus (Madsen, 1976B) alone among the theropods show such a rise, although some (e.g. Tyrannosaurus) exhibit a downcurving of the ventral margin toward the symphysis. The smooth medial and lateral surfaces of the dentaries are reasonably well preserved and show neither median longitudinal bars nor interdental plates. On the lateral surface a row of foramina lies 1.5 cm below the dorsal margin posteriorly. Surangular.— A fragment 5 cm long of this element is preserved (Text-fig. 4). Comprised are a portion of the articular facet for the quadrate, the facet for insertion of the M. adductor mandibulae externis superficialis, and a small portion of the lateral surface. Because unbroken surface can be traced in a transverse plane all around the piece just anterior to the quadrate contact it is probable that a surangular foramen was present. A lateral buttress lay just above the foramen suggesting the presence of a lateral fossa as in the dromaeosaurids (Ostrom, 1969). Teeth.— Six nearly complete crowns are preserved in the two maxillae (Text-fig. 5). These are the first (1.6 cm in length), second (4.3 cm), and fourth (4.7 cm) right, and the first (1.8 cm), second (3.5 cm), and fourth (4 cm) left. The third on each side is represented by a partially erupted crown. All maxillary teeth are similar in form and show 15 serrations per 5 mm along the anterior carina, and 12 to 18 per 5 mm along the posterior. Four of these teeth lay anterior to the antorbital recess. The first shows no wear, and the crowns of the other maxillary teeth are uniformly 2.5 times as long as that of the first. A tooth, adhering to the left maxilla, of different form from the maxillary teeth is assumed to be a premaxillary tooth. The crown is 1.2 cm long, shorter than those of the maxillary teeth, and is similar in form to the premaxillary teeth of tyrannosaurids and Dromaeosaurus with carinae at the posterolateral and posteromedial corners. The tooth is D-shaped in cross section and differs from Tyrannosaurus premaxillary teeth in being shorter anteroposteriorly and in lacking serrations. All but the first dentary teeth are similar to those of the maxilla, but smaller. The largest preserved is 3.2 cm high, and although another appears larger (3.7 cm) this is due to slippage partially out of the alveolus. The first dentary tooth (crown 0.9 cm long) is smaller than the second, and its anterior carina is displaced medioposteriorly, the serrations running along the medial surface of the tooth. None of the dentary teeth are D-shaped in cross section. The first tooth resembles the symphyseal premaxillary teeth of Deinonychus antirrhopus (Ostrom, 1969, fig. 24D) and the first dentary tooth of Dromaeosaurus. The second dentary tooth (1.9 cm high) is smaller than the succeeding teeth which range from 2.4 to 3.2 cm in length of crown. The more posterior of the dentary teeth show 15 to 20 serrations per 5 mm along the anterior carina, and 14 to 15 along the posterior: those of the first tooth are too worn for a count. Endocranial mold.— The partial mold (Textfig. 6) has been prepared from the frontals and parietals. Just anterior to the cerebral hemispheres is a constriction of the olfactory passage, which then abruptly widens anteriorly. Such a constriction is also present in the olfactory passages of Allosaurus and Tyrannosaurus (Osborn, 1912), Tarbosaurus (Maleyev, 1965) and Ceratosaurus (Marsh, 1896). In both Tarbosaurus and Tyrannosaurus the constriction is less abrupt than in the Jordan theropod, which more resembles Ceratosaurus in this respect. The cerebral hemispheres are prominent, bulging both dorsally and laterally, but not as much enlarged as in Stenonychosaurus (Russell, 1969, fig. 3C). A slight expansion of the right side posteroventral to the cerebral hemisphere probably represents the right optic lobe, which was relatively larger than in Allosaurus, Stenonychosaurus or Tyrannosaurus, more like that of Tarbosaurus (Maleyev, 1965). The mid- and hindbrain region is distinctly lower than the forebrain region and flatter. This is in marked contrast to the conditions in Tarbosaurus and Tyrannosaurus where there is a slope upward to peak beneath the supraoccipital crest and then downward toward the foramen magnum. In the Jordan theropod the crest was considerably to the posterior of this peak of the endocranial cavity, giving the profile an appearance different from those of the tyrannosaurids. The descending posterior surface of the forebrain region exhibits a small projection (corresponding to the previously described pit of the parietals) similar to, but smaller than, that shown by the endocranial mold of Dromiceiomimus brevitertius (Russell, 1972). It presumably housed a parietal organ. Nerve foramina are not evident on the mold (the region preserved being dorsal to them), nor are there any dorsal channels opening from the endocranial cavity as in Tyrannosaurus (but not Tarbosaurus). DISCUSSION Maturity of the specimen.— The size of the Jordan theropod suggests that it might represent an immature tyrannosaurid. Recent work (Rozhdestvenskii, 1965; Dodson, 1975B) indicates that immature dinosaurs are often referred to new taxa rather than recognized as immature. The best method of showing the immaturity of a given specimen is the presentation of a growth series, as is known for Allosaurus (Madsen, 1976A) and Tarbosaurus (Rozhdestvenskii, 1965). Lacking such a series, one may extrapolate from known ontogenetic trends of the skeleton or look for features taken to be indicative of immaturity. Neither of these latter methods is conclusive for there is no certain way of identifying an immature individual as such from a single skeleton, given the continuous growth (implying open sutures) and the usual lack of terminal epiphyseal bones of reptiles (Dodson, 1975A). In the absence of a growth series characters of the Jordan theropod must be compared with predictions from known ontogenetic trends. As few such trends have been inferred in theropods, those of crocodilians (chosen because they exhibit closer phylogenetic relationship to theropods than other living reptiles and a more conservative structure than birds) are used. Crocodilians exhibit three trends of interest here: increase in relative length of the snout with age, decrease in separation between the supratemporal fenestrae with age, and increase in depth of dentaries with age (Dodson, 1975A; Kalin, 1933, 1955). Similar trends have been indicated in lambeosaurs (Dodson, 1975B). The first trend can also be demonstrated for tyrannosaurids, in Tarbosaurus and Tyrannosaurus (Text-fig. 7). In Albertosaurus libratus the smallest skull, of AMNH 5664, has suffered dorsoventral crushing of the snout (Gilmore, 1945) which may conceal such a trend. The preserved portion of the snout of the Jordan theropod is longer relative to its height than that of any tyrannosaurid (Textfig. 7), suggesting that it is not an immature tyrannosaurid. The parietals of the Jordan theropod indicate the supratemporal fenestrae were more widely separated than in mature tyrannosaurids, suggesting that it may have been immature (or small). The dentary of the Jordan theropod is shallower with respect to the length of the maxilla (anterior to the antorbital recess) than in any tyrannosaurid (Text-fig. 7), but is most closely approached by that of PIN 552-2, an immature Tarbosaurus bataar (the type of “ Gorgosaurus novojilovi ”). This also suggests that the Jordan theropod was immature (or small). Other features consonant with the interpretation of immaturity are: the smooth nasals, the lack of ossification ventral to the cristae cranii, the elongate form of the frontals (Textfig. 8) and possibly the smooth naso-maxillary union. Yet all of these can also be found in adults of smaller taxa. Several authors (e.g. Ostrom, 1969; Colbert and Russell, 1969) have used serration count as a diagnostic character of theropods. The number of serrations per 5 mm of crown is greater in the smaller genera (Ostrom, 1969, Table 2). As far as I know only Gallup (pers. comm., 1975) has tested this trend, with isolated teeth of different sizes attributed to Acrocanthosaurus. He has found that smaller teeth have the greater serration count. Although this suggests that the serration count may change in ontogeny, other explanations are possible and more work on this point is desirable. The Jordan theropod shows a higher serration count than Albertosaurus and Tyrannosaurus (Ostrom, 1969), possibly consonant with interpretation of immaturity, if Gallup’s trend is substantiated. These considerations suggest, but do not prove, that the Jordan theropod may have been immature. Taxonomic affinities.— The Jordan theropod shares several characters with mature tyrannosaurids: the surangular foramen and buttress, D-shaped premaxillary teeth, and W-shaped naso-frontal contact. Interpretation of it as an immature tyrannosaurid allows accommodation of a suite of characters in which it differs from adult tyrannosaurids such as the smooth nasals, acute anterior angle of the maxilla, shallow dentary and shallow angle of the symphysis (all found in AMNH 5664). But other characters cannot be accommodated. Comparison with the two contemporaneous well known tyrannosaurids, Albertosaurus lancensis and Tyrannosaurus rex, shows that both have a deeper maxilla than the Jordan theropod (Text-fig. 9). This is especially true of the juvenile maxilla of T. rex recently described by Lawson (1975), which also differs from the Jordan theropod in that the maxillary fenestra is adjacent to the anterior margin of the antorbital recess in T. rex. The most similar tyrannosaurid maxilla is that of AMNH 5664, the immature Albertosaurus libratus. Even though this maxilla has suffered dorsoventral crushing (of which there is no indication in the Jordan theropod) it is still higher than that of the Jordan theropod. Compared to those of the Jordan theropod, the frontals of tyrannosaurids are relatively thick (cf. Osborn, 1912, Pl. III). Admittedly immature tyrannosaurids undoubtedly bad thinner frontals than adults, but those of LACM 23845 (tentatively attributed to A. lancensis) are 1.4 times the length of those of the Jordan theropod, but 2.5 times the thickness. Lack of invasion of the frontals by the supratemporal recesses may indicate immaturity, but invasion is present in AMNH 5664, and lacking in several large theropods, e.g. Chilantaisaurus (Hu, 1964), Indosaurus (v. Huene and Matley, 1933) and Labocania (Molnar, 1974). The postorbital contact of the frontal is basically similar in the four well known tyrannosaurid genera, subcircular in form and interlocking. This is quite different from the simple, anteroposteriorly elongate concavity of the Jordan theropod. The form of the prefrontal contact of the frontal in tyrannosaurids is not described in the literature, but two specimens, LACM 23845 and MMS 51-2004 tyrannosaurus sp.), exhibit this surface. In both it is dorsoventrally, not anteroposteriorly, elongate and in MMS 51-2004, an interlocking suture not a simple concavity. Taken together these characters indicate that the Jordan theropod, while showing a superficial resemblance to an immature tyrannosaurid, cannot reasonably be assigned to any known tyrannosaurid genus. Of the other late Cretaceous theropods, many, e.g. Alectrosaurus, Chingkankousaurus, Coelosaurus, Dryptosaurus, Macrophalangia, Pneumatoarthrus lack material in common with the Jordan theropod and cannot be compared. Others, the ornithomimids, saurornithoidids and oviraptorids, are obviously different. The dromaeosaurids are the most similar. Resemblances of the Jordan theropod to dromaeosaurids include the surangular foramen and buttress, smooth and thin parallelsided nasals, absence of interdental plates in the dentaries (present in tyrannosaurids), serration count, shallow mandibles, thin frontals and lack of D-shaped anterior dentary teeth. The forms of the prefrontal and postorbital contacts of the frontals of dromaeosaurids are poorly known. Figures in Colbert and Russel
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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