Xenoposeidon is the earliest known rebbachisaurid sauropod dinosaur

Xenoposeidon proneneukos is a sauropod dinosaur from the Early Cretaceous Hastings Group of England. It is represented by a single partial dorsal vertebra, NHMUK PV R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with the rebbachisaurid diplodocoid Rebbachisaurus garasbae from the mid-Cretaceous of Morocco: an ‘M’-shaped arrangement of laminae on the lateral face of the neural arch. Following the more completely preserved R. garasbae, these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its inferred elevated parapophysis, the holotype vertebra is considered a mid-posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the Berriasian–Valanginian (earliest Cretaceous) Ashdown Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon’s true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible.

Cervical tuberculosis associated with cervical pain and neurologic deficit: a case report and literature review

BACKGROUND CONTEXT

Isolated tuberculosis (TB) of posterior elements of the cervical spine is extremely rare. Only few cases are reported in literature, but none describe isolated spinous process and laminae involvement without TB in any other part of the body.

PURPOSE

To report a case of isolated TB involvement of the spinous process and right laminae of C2 combined with atlantoaxial luxation.

STUDY DESIGN

A case report of isolated spinous process and right laminae TB of C2 combined with atlantoaxial luxation.

PATIENT SAMPLE

A 20-year-old male farmer complained about a 2-month history of aggravating neck pain, a 1-month history of a slowly growing lump at the back of the neck, and numbness and weakness of the right arm that had gradually progressed to involve all the limbs for 2 weeks before presentation.

OUTCOME MEASURES

X-ray and computed tomography of cervical spine and Frankel grading of neural function are included to evaluate the therapeutic efficiency.

METHODS

Computed tomography scans showed flake-like bony destruction located in the spinous process and at the right laminae of C2. Magnetic resonance imaging (MRI) showed a large swelling posterior to C2 and atlantoaxial luxation-induced distinct compression of the spinal cord. The patient underwent 2 weeks of skull traction and quadruple anti-TB treatment before surgery.

RESULTS

The patient underwent surgical treatment that included posterior radical debridement, decompression, internal fixation with a screw-rod system from C1 to C4, autologous bone grafting, and fusion. The patient gained normal neural function and returned to work 1 year after surgery.

CONCLUSIONS

Tuberculosis of the posterior elements of the upper cervical spine is very rare and potentially dangerous. Computed tomography and MRI are very useful and important for correct diagnosis. Prompt medical and surgical treatment may avert potential catastrophic event in these cases.

Nutrient foramen location on the laminae provides a landmark for pedicle screw entry: a cadaveric study

Background

Nutrient foramina are often encountered around the entry point of pedicle screws. Further, while probing the pedicle for pedicle screw insertion around the nutrient foramen, bleeding from the probe insertion hole is often observed. The purpose of this study was to investigate the frequency of occurrence of nutrient foramina, the association between the nutrient foramen and pedicle, and the safety and accuracy of cervical and thoracic pedicle screw placement using the nutrient foramen as the entry point.

Methods

We identified the location of the nutrient foramina for the dorsal branches of the segmental artery and their anatomical association to the pedicles and bony landmarks in the vertebrae for C3–T12 in seven cadavers. We also determined the frequency with which the nutrient foramina were present in 119 cadaveric vertebrae. We identified the pedicle location, base of the superior articular facet, and lateral border of laminae with respect to the nutrient foramen.

Results

The overall presence of the nutrient foramina was 63% (150/238) in the specimens, with 60% (42/70) and 64% (108/168) identifiable in the cervical and thoracic vertebrae, respectively. In the cervical vertebrae, the nutrient foramen was located on the outer wall of the pedicle and was positioned between the cephalad and caudal walls. In the thoracic spine, 98% (106/108) nutrient foramina were located inside the pedicle walls.

Conclusions

Our study findings confirm that the location of the nutrient foramen can be used for identifying the entry point for pedicle screws. In the cervical vertebrae, the nutrient foramina are located lateral to pedicle but within the cranial and caudal margins. In the thoracic vertebrae, the nutrient foramina are located in the medial and caudal regions of the pedicle. Thus, to decrease the risk of overshoot, the entry point for thoracic pedicle screws should be positioned a few millimeters cephalad and lateral to the nutrient foramen.

Supporting Limb Laminitis

Supporting limb laminitis (SLL) is a relatively frequent complication of painful limb conditions that alter normal weight-bearing patterns in horses. New evidence suggests that a lack of limb load cycling activity (normally associated with ambulation) interferes with normal perfusion of the lamellae in these cases, resulting in ischemia and dysfunction/death of cells critical to the mechanical function of the lamellae. Excessive weight-bearing load drives the progression to overt acute laminitis in the supporting limb. Monitoring and enhancement of limb load cycling activity are key strategies that may lead to successful prevention of SLL by ensuring adequate lamellar perfusion.

Initial decomposition of floating leaf blades of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Menyanthaceae): causes, impact and succession

Background

During a study on the outdoor floating leaf blade production of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Fringed Water Lily), initial leaf blade decomposition was studied by simultaneously measuring infected, damaged and lost area of floating leaf blades.

Methods

Data on initial decomposition over time were collected for all leaves during one growth season in four plots: two in outdoor mesocosms and two in an oxbow lake. Each leaf was tagged uniquely upon appearance in a plot. The vegetation in the mesocosms differed with respect to plant species, one contained a monoculture of N. peltata and the other N. peltata associated with Glyceria fluitans (L.) R. Br. and G. maxima (Hartm.) Holmb. The lake plots were situated within a monospecific N. peltata stand, differing in depth and position within the stand. Leaf length, visually estimated percentages of damaged area for each damage type, and decay of the tagged leaves were recorded bi-weekly. When the leaf blades sunk under the water surface or disappeared completely, they were no longer followed. Under water the leaves decayed and were consumed by snails completely, so contributing to the detritus food chain.

Results

The observed causes of damage on floating leaves were consumption and/or damage by waterbirds (Fulica atra), pond snails, caterpillars (Elophila nymphaeata, Cataclysta lemnata), chironomid larvae (Cricotopus trifasciatus), infection by a phytopathogenic fungus (Septoria villarsiae), senescence by autolysis, and microbial decay. Successional changes in causes of leaf decomposition and impacts of different causes are discussed.